A Bread Time Story

Artisan Bread from the King Arthur Flour No-Knead Crusty White Bread Recipe

The minute you show up somewhere with a little flour on your shoulder, the questions begin: "Can you tell me how to make bread? I'll kill the yeast. . . My spouse punches the dough so hard it won't rise. . . overall I'm just afraid of dough."

I get these comments because I'm often out in public, heedless of the patches of crusted dough on my forearms and flour trails down my jeans, sporting a baseball cap that says "Bake."

If you want to make good bread, fear not. Mastering artisan bread is like learning to dance - you may never be a great dancer, but you can improve, you can always improve.

There is a recipe you can make without killing the yeast, punishing the dough or messing it up in other unimaginable and unkind ways. It's my house favorite and soon may be yours.

The King Arthur Flour No-Knead Crusty White Bread is the recipe we've all been looking for. It excels on so many levels home bakers care about - ease of method, visual appeal and crackling good flavor. To get the best flavor, allow a few days on it, don't rush it. Good bakers mix a little and ferment a lot.

The flour to liquid ratio in this recipe is important. If you measure flour by sprinkling it into a measuring cup and sweeping off the excess, use 7 1/2 cups of flour. If you measure flour by weight (and I wish you would), use 32 ounces. If you understand baker's percent math, I've added the ingredient ratio percentages, along with additional wording here and there.

King Arthur Flour No-Knead Crusty White Bread

 

Yield: 3 loaves

24 ounces lukewarm water                 (75%)

32 ounces unbleached all-purpose flour         (100%)

2 tablespoons kosher salt                    (1.8%)

1 ½ tablespoons instant yeast              (1.6%)

¼ cup milk for washing

Combine all ingredients in a large mixing bowl or large (6-quart) food-safe plastic bucket. With a wooden spoon, stir together to get a sticky, rough dough. If using a stand mixer, use a paddle attachment and beat on medium speed 30-60 seconds. Cover bowl with plastic wrap, allow dough to rise at room temperature for 2 hours.

Now refrigerate for at least 2 hours, or up to 7 days (by day 4 it has a good tang, so this may be the best stopping point for continued retardation; you decide). The longer you keep it in the fridge, the tangier it'll get. (If pressed for time, you can mix dough, then place directly in the refrigerator.)

When ready to use, pre-shape this dough straight from the refrigerator. Round it into a ball (boule) shape.

Allow dough to rise in either a flour-dusted wicker banneton, a cloth-lined basket (seam side up) or on a piece of lightly greased parchment on a sheet tray (seam side down). Cover with oil-sprayed plastic wrap to prevent skin from forming. Allow dough to rise at least 60 minutes (or longer, as needed) at room temperature.

Preheat oven to 450 while dough rises. (I've found that 3-4 hours of rise time is about right, but that's in my kitchen. Yours may be different.)

Place a shallow metal pan or cast iron skillet in oven while preheating. Have a cup of water ready to add to pan when you load the loaves.

Just before baking, score loaves using a French lame razor blade or sharp knife, then using pastry brush, lightly brush loaves with milk.

Place bread in oven, pour water into hot pan and close door quickly.

Bake 25-35 minutes, or until deep golden brown. If using a digital thermometer, you want at least 200 degrees. Remove bread from oven, cool on rack. Allow bread to cool completely before slicing. Store leftover bread at room temp in a plastic bag; do not refrigerate. Freeze leftovers for breadcrumbs, croutons, bread pudding and toast.

Scaling: Total dough weight is 51.50 ounces. For 3 loaves, scale at 17 ounces each.

*Note: In recent years bakers have started placing bread dough in a special "cloche" dome or a cast iron/enamelware Dutch oven for baking. Such containment helps re-create the hearth baking of Old Europe and concentrate the heat so it's consistent around the loaf, with the added benefit that evaporating water can't escape, so it helps steam the loaf. (So you can skip the hot pan and water for steaming if using a dome.) The results are golden, brown and delicious. You can also use a baking stone and turn the Dutch oven upside down over the dough. Be sure to preheat the stone and Dutch oven before baking.

And yes, I do bake my loaves in the cast iron Dutch oven. The loaves look fuller and rounder, and the top crust browns in classic, artisanal style. There's no worry about steaming the dough. (But please use caution when lifting the dome after baking, as you can steam your fingers. Tilt the dome away from you when lifting.) Isn't it freeing to no longer squint through how long to mix the dough on a stand mixer? By allowing this dough to hang out a few days in the fridge, the mixing happens passively as water migrates through the gluten network. Acids that contribute flavor build up. All's right with the world.

To go deeper into the chemistry of artisan bread, check out Jeffrey Hamelman's book "Bread: A Baker's Book of Techniques and Recipes" (second edition). Hamelman, baking director of King Arthur Flour, is a Certified Master Baker who helps coach Team USA when they compete in the Coupe du Monde de la Boulangerie, the bread Olympics held in Paris.

I like what he said about baking when accepting the Golden Baguette Award, the highest bestowed by the Bread Bakers Guild of America: "We are lucky to be bakers, doing this good work that requires our minds, hands and hearts, because we
 have a lifelong opportunity to grow."

A sourdough made with stiff culture, from Hamelman's book "Bread," first edition

*With special thanks to King Arthur Flour for permission to reprint the recipe. To learn more, visit King Arthur Flour.

A Better Chocolate Chip Cookie, Harvard Style

Here's a hybrid chocolate chip cookie for keeps

The Harvard online food science class has terrific lectures and demos. One of the best is from America's Test Kitchen, on how to make a better chocolate chip cookie. Tossing aside the method on which the Nestle Toll House classic is based - the creaming method - they revamped steps to make a flavorful, crisp cookie on the outside with a tender interior.

I took it another step, preferring the ingredients of Shauna Niequest's "Gaia Cookie" recipe from her book "Bread and Wine."

Here's the hybrid featuring a method from America's Test Kitchen and ingredients adapted from Niequest's work.

If You Give Harvard a Cookie

Ingredients

8 ounces unsalted butter, divided use

1 ½ cups brown sugar

1 whole egg plus 1 egg yolk

2 tablespoons vanilla extract (I recommend Nielsen-Massey Madagascar Bourbon Vanilla Bean Paste)

1 ½ cups all-purpose flour

1 ½ cups rolled oats

1 teaspoon baking powder

1 teaspoon baking soda

1 teaspoon salt

1 cup walnuts, toasted and chopped

1 cup good quality chocolate such as El Rey, Callebaut, Valrhona, Guittard, chopped

1 cup chopped dates, raisins, dried cherries or dried cranberries, or any combo

kosher or a good-quality sea salt (optional)

Preheat oven to 375

Method

In a small saucepan, melt 6 ounces of the butter over medium heat, swirling the pan occasionally until the milk solids begin to brown and the butter turns a nutty color. Pour through a strainer into a glass bowl (to remove brown bits), then add the other 2 ounces of butter and stir to cool (this adds additional water lost during the melting and helps cool the mixture, ATK says).  Add the brown sugar and stir.

Allow this mixture to rest 10 minutes (to give the sugar time to invert); stir occasionally. Meanwhile in a separate bowl, whisk together the dry ingredients including flour, oats, baking powder, baking soda and salt, set aside.

To the butter and sugar mixture, whisk in 1 whole egg, and when incorporated, add the yolk and whisk it in. Add vanilla and whisk in. (That's right, no stand mixer needed!)

Add the dry ingredients to the wet and stir. Now add the nuts, chocolate and dried fruit.

On a baking sheet lined with parchment or a silpat, scoop out dough using a scoop that holds about 3 tablespoons. Place cookie dough about 2 inches apart. Allow the sheet pan to rest in fridge at least 10 minutes to chill the dough before baking. Just before baking, sprinkle the dough with kosher salt or sea salt. This adds a wonderful finish (but do it lightly).

Bake at 375 for 10-12 minutes, rotating the pan halfway through.

Dough may remain a bit domed from scooping, so rap the pan a few times gently on the work surface after baking, and the cookies will flatten slightly. Or, flatten them slightly with the palm of your hand just before baking.

Tip: Make sure the chocolate is chopped down to bits about the size of Toll House chips. If they are too large or you add too much chocolate, the chocolate can spread the batter into a flat disk.

Dried Fruit Tip: Try soaking the dried fruit in hot water (or liqueur!) to rehydrate it before adding it to the dough. Dried fruit tends to get even drier when baked, so plump it up, then drain off the liquid before using in the dough.

Get doughing!

Week 10: Fermentation, Harvard Style

Fermentation, such as with yeast in this pepper wreath, helps round out Week 10

And then we came to the end. In the final week of the Harvard online food science class, the subject header was "fermentation," but the introduction of a little something called "transglutaminase" was a magic carpet ride that transported us to the world of crazy enzymes.

Two famous creative guys fired up the week's lecture series: Wylie Dufresne of wd~50 and David Chang of Momofuku. Chef Wylie and colleague Ted Russin from the Culinary Institute of America talked about the enzyme transglutaminase, or "meat glue," that just may be the biggest "oh, wow" concept of the whole course. These guys are making what you've never thought of before - noodles entirely of shrimp, and pasta made of carrots. They also show how they "glue" cuts of steak and fish together, a powerful concept. It means there's no trim loss. You can stick meat together when you apply an enzyme paste, roll it up like cookie dough, and slice it in perfect rounds. That's good for the guest and good for the restaurant. You just knew science was cool. Week 10 felt like the adage of old, save the best for last.

Over at Momofuku, David Chang and staff showed how to create fermentation reactions that lead to new foods like their hozon (Korean for "preserve") and a new spin on kimchi. They also made a critical point - do not try this at home. They've spent countless hours working in specific conditions to ensure food safety while tweaking around with enzymes. Research if you must, but always mind the safety.

There's also an excellent section on how enzymes cause browning in food. You know this if you've cut up an apple. Many fruits have an enzyme called polyphenol oxidase. This enzyme reacts with phenolic compounds in the presence of oxygen to make that brown discoloration when you cut. That's because the fruit normally keeps polyphenol oxidase and phenolic compounds separate in cell walls, but once you break those walls by cutting or bruising, they come together, hit the oxygen and turn everything brown. How can you decrease this rate of browning? Denature that enzyme! Do it by adding acid such as lemon juice, or with very high temperature (cooking it). Or you can make the enzyme less active by using low temperature, limiting exposure to oxygen or using high salt concentration. In pastry school when making tart tatin, we'd slice up the apples but then drop them into an acidified solution of lemon juice and water. That kept them out of the oxygen and into an acidic state.

There's another reaction that happens because of cell damage - pungent, flavorful fumes, like when you slice up garlic and onions. That enzyme is alliinase. Now sometimes you get a recipe that has you finely chop or mince garlic and onions to increase the cell damage, so you gain more flavor. Or you get a recipe that calls for garlic and onions to be roasted or sauteed at high temperature to decrease their pungency by inactivating the enzyme.  

Tip No. 1: A sliced garlic clove will have less flavor in the dish than a minced one - and now you know why!

Tip No. 2: ATK says the only way to truly protect your eyes from tearing up when chopping onions is with goggles. 

The week also covers microbes, which impact baking and fermentation for things like cheese, wine and vinegar. You also get an equation that allows you to figure out just how many microbes are present in a food, based on how they grow exponentially.

Equation of the Week: N(t) = Noe to the kt power, where No is the initial number of microbes and k is the rate of growth.

A-Ha Moment of the Week: America's Test Kitchen explains why pesto darkens (remember browning caused by enzymes?) Adding parsley to the pesto will help keep the pesto bright green. Parsley contains vitamin C, and since vitamin C is acidic, you see why parsley can help denature the enzymes.  

Science is golden!

Next: My Final Project (and it involves Velveeta)

Week 9: Baking, Harvard Style

Getting the oven heat just right makes all the difference in pretty little feet for macarons

And so the Harvard online food science class finally reaches my heart's desire, the world of sugar and fat. It makes sense that the course has waited so long to get to this area of interest, since baking involves the concepts of elasticity, viscosity, gelation, emulsions, heat transfer and solubility, all food for thought in the course to this point.

Just what constitute baking? Call it the indirect application of heat to food. In other words, if you've "cooked" ceviche using lime juice, that's not baking. To dig into this further, we learn how the elastic properties of dough are one of the central features of baking. Three things give rise to dough's elasticity and how it changes: 1) the properties of gluten (found in flour) 2) the elastic network of eggs 3) starches and sugars (and how they behave). Viscosity in baking is all about how dough rises and expands. Emulsions are everywhere in baking - in cake batters, cookie doughs, souffles, dessert sauces and even chocolate ganache. Let's not forget those all-important chemical reactions (since this is food science), including release of gases (from chemical leaveners and yeast) and solubility of ingredients, like sugar in water for a simple syrup. What a mouthful, all these concepts of baking.

There are wonderful demos during this week, many of them from Joanne Chang, owner of Flour Bakery in Boston and Cambridge, who walks us through a yellow cake; a good pie dough; pate a choux, pastry cream and caramel for building a croquembouche, and artisan bread with a great scoring pattern on its top. Here's an attempt to capture just a few of the "a-ha" tips from Week 9.

A-Ha!

1) The creaming method is called the creaming method because when you beat air into butter, the mixture turns the color of cream. How did I get through baking & patisserie school without hearing THAT?

2) Why should eggs for a recipe be at room temperature? Because if they're cold, they introduce a temperature difference to the mixture. Same with butter. Adding ingredients that are too cold can break a batter's emulsion; we learned that in school. So the idea is, keep all your ingredients at room temperature (if you have time; I've rushed a few egg whites through for macarons).

3) What's the "3-2 method"? It stands for alternating wet and dry ingredients into a batter. The dry ingredients represent the "3" and the "2" is for the wet ingredients. So you add a third of the dry ingredients, then half the wet, then a third of the dry, then the other half of the wet, and finish with the last third of the dry. Start and end with dry, there's a good chef.

4) Know your acids in the recipe, because they all contribute to the activation of chemical leaveners to release carbon dioxide (and cause leavening). The list: chocolate, molasses, sour cream, coffee, buttermilk, vinegar and lemon juice, to name a few.

5) Did you know: A souffle that has deflated will rise again if you put it back in the oven, where air and moisture will help it expand. Something else to note about a souffle: The base must be overflavored to compensate for its dilution by egg whites and air. Meaning, use more vanilla than you think.

6) Why is a sourdough starter good for croissant dough? It acidifies the dough, which decreases the dough's elastic modulus. All I know is, it's always easier to roll out than just plain croissant dough. As it turns out, when you lower the pH of the dough (by adding sourdough starter), the glutenin molecules become more charged, so they repel each other, which lowers the strength of their interaction and the gluten network (glutenin and gliaden combine to form the gluten network) and the dough becomes more tender. Like I said, the dough is easier to roll out if you add a sourdough starter.

7) There are 2 kinds of browning reactions that give those lovely colors and tastes to baked goods: caramelization and Maillard Reaction. Caramelization causes browning when sugar is heated and the sucrose molecule separates into fructose and glucose. The caramelized result tastes buttery and nutty. This occurs at about 165 degrees Celsius or higher. The Maillard Reaction happens as heat is applied and sugar molecules react with amino acids in protein molecules. This happens above 120 degrees Celsius. Good old Dulce de Leche is an example of a Maillard Reaction of a milk and sugar solution. So is a browned steak.

My Favorite A-Ha Moment of the Week: How to make a better chocolate chip cookie without the creaming method. This method from America's Test Kitchen is so good, it deserves a separate post, so visit the chocolate chip cookie here.

Equation of the Week: If I understand my notes correctly, we used formulas related to the concepts that have been covered throughout this course, i.e., we repurposed the elastic modulus, the formula for determining cross-link distances and so on. Importantly, we did calculate the exponential growth of yeast. It involves huge numbers so you need one of those exponential calculators to do the math.

I'd rather build a croquembouche.

Final Week: Fermentation!

Week 8: Emulsions & Foams, Harvard Style

Did you know: Truffle centers made of chocolate ganache are an example of an emulsion?

In Week 8 of the Harvard online food science class, we finally get into something that looks familiar from culinary school. It's the idea that not all foods dissolve into each other. Some exist in suspension, that is, when forced together, they make an emulsion. You've eaten an emulsion if you've ever had mayo or hollandaise, but cake batters, cookie doughs, souffles, vinaigrettes, whipped cream and even chocolate ganache are also emulsions.

Let's define emulsion - it's a state in which drops of one immiscible fluid are mixed into a second fluid. If you pour oil into vinegar and  shake the bottle vigorously, you suspend droplets of oil into the vinegar  to make a vinaigrette. They'll mix together so you can dress your salad, but they won't stay together forever. Oil is lighter than vinegar, so little oil droplets that were in suspension end up floating to the top, where they begin sticking together with other oil droplets on the same journey. Eventually this oil mass separates from the solution and stays on top until you do something about it. (That's when you have to shake shake shake shake the bottle again to break the oil back into small droplets.) In this case, the vinegar is known as the continuous (usually fluid) phase, and the oil is known as the dispersed phase (because it gets dispersed in droplets throughout the vinegar). That's one kind of emulsion - but not the only one.

Now why do bottled dressings from the fancy food store seem to hold together and avoid separation? They may contain surfactant ingredients. A surfactant - surface active molecules - likes both water  and oil. Surfactants sit at the interface, or the surface, between the two fluids and help hold onto both the oil and the water in a chemistry kind of way. They also prevent droplets from colliding with each other and forming larger droplets which, if left to their own devices, can start to separate out of the solution. Lecithin in eggs is an example of a good surfactant - and it's why egg yolks can help hold an emulsion together (one of the go-to fixes of saving a broken Hollandaise is to beat in another egg yolk).

A foam represents the same idea of one substance suspended in another, but instead of a liquid dispersed in another, you whip air bubbles into a liquid, as in a souffle. These bubbles can also "cream," or rise to the top, where they destabilize more easily and pop, there goes that emulsion.

Did you know: Nitrous oxide, which is in those cool canisters that The Buck uses to add whipped cream to your latte, turns into liquid under pressure? When forced through the canister of cream, it becomes an emulsion of two liquids.

Chocolate ganache is another type of emulsion, where particles are dispersed into a liquid. In this case, cocoa solids in the chocolate are mixed with the continuous phase of cream. Solid particles in a fluid are called colloids. These colloidal particles like to exist at an interface between two fluids (think of melted chocolate and cream as the two fluids).

If you've ever tried to mix cream into chocolate and watched it turn oily, you've seen an emulsion break. The go-to fix is to bolster the continuous phase - the cream - by adding more cream and stirring heartily while whispering encouragement.

How is it that emulsions fail anyway?

In the liquid in liquid emulsion, oil and water have different densities. Eventually the oil will do what's known as "creaming," by rising to the surface of the water. The Week 8 review sheet calls this "separation of phases by gravity due to density differences." Oh, gravity. To get the oil and water back together, you have to whip this solution to break the oil into small droplets that recombine into the continuous phase of water.

Then there's "coalescence," where two oil drops come together and form a larger drop; it's small droplets that give an emulsion its character and smooth mouthfeel. Too much heat can also break an emulsion, which you know if you've ever left a Hollandaise over a bain marie of steaming water and your eggs coagulated, forcing liquid out of the egg protein network like wringing a sponge.

And then there's something called Ostwald Ripening. It's the transfer of the fluid from one drop to another. There's a driving force and increased pressure to drive the fluid from the small drops into large drops. My notes here say: Aggregates of surfactant can swell slightly, absorbing some oil, and can transfer that oil across the continuous phase from one small drop, where the pressure is large, to a large drop where the pressure is small. Small droplets get smaller and large drops get larger. Eventually the small droplets disappear. I had to look at the Week 8 review sheet on this. It says, "Despite an energy barrier, individual molecules from the dispersed phase occasionally dissolve in the continuous phase, through which they can travel to other droplets/bubbles. Over time, there is a net movement of molecules from small bubbles/droplets to larger ones." There you have it.

Sometimes the continuous and dispersed phases change. The continuous becomes the dispersed, and the dispersed becomes the continuous. You've seen this if you've badly made a cookie batter, where you had a water-in-fat emulsion while creaming your ingredients, suddenly the emulsion breaks and you have the reverse - a fat-in-water emulsion where bits of fat are floating around in your solution.

Each type of emulsion break can often be fixed, and it usually involves agitation to break big drops into little drops via whisking, sometimes includes heating over a hot water bath so the continuous phase becomes more fluid, along with vigorous whisking (good for buttercreams); and sometimes you just have to add more continuous phase, such as adding more cream to ganache, to help suspend those cocoa solid colloids in the cream.

It is not scientifically established that hurling curses at the mixture can right the wrongs, but encouraging words are never discouraged, so try it.

Equation of the Week: E = 0/r (phi - phi c), where E stands for emulsion, r is the radius of the droplets, phi c is the critical volume fraction and o is the interfacial tension. To understand this, you need a Harvard professor, so take the course and do the legwork.

Ah-hah Moment of the Week: To freeze egg yolks, add 1/4 teaspoon of simple syrup per yolk. (Simple syrup with a ratio of two parts water to 1 part sugar). This lowers the freezing point of the eggs and prevents ice crystals that disrupt the protein network.

Next Week: It's Baking!

Week 7: Viscosity and Polymers, Harvard Style

Classic crepes are an example of a liquid batter that thickens during cooking to the point where there is no fluid flow, unless you count the Grand Marnier sauce.

Viscosity is a word that sounds like a bitter subject - but it introduces an engaging week of food science that's all about thickening power. Hello sauces!

Viscosity is the resistance of a fluid to flow. The larger the food molecules, the slower the flow. The more resistance to flow, the higher the viscosity.

Where this truly matters is in sauce-making, right? There are four basic ways to change sauce thickness: 1) reduction 2) adding starch 3) making an emulsion 4) modernist thickeners

Diving into this rich pool of intrigue, we begin with reductions. So in a reduction, you have a sauce on the stove and you keep heating it to reduce the available liquid via evaporation. As liquid goes down,  the food molecules become more concentrated and bump into each other, which slows the sauce's ability to flow. In a classic reduction, you reduce by half - and it only works because there were already enough molecules in the pan to cause thickening. So by increasing the concentration as you drove off the water, resistance to flow increased. Voila!

Now when you add a starch to your sauce, like cornstarch or flour, you're adding larger molecules into the food, and this also impedes flow. Think of a roux - butter and flour. You heat the starch in the flour so it hydrates and gelatinizes (and by doing so, those molecules swell and get bigger). The starch molecules become sticky polymers and rub against each other, creating the sensation of thickening. The problem is, you need a lot of flour to get this thickening, and if you use too much, your sauce gets rubbery - and those starch molecules can dilute desirable flavors, too. Pity the poor bechamel sauce if this happens.

Up next is the emulsion technique, like when you make mayonnaise. When you add oil to the eggs, you suspend tiny droplets of one phase of a liquid into another. The droplets become like people on a subway platform, running and bumping into each other and trying to get out of each others' way. The more you add, the stiffer everything becomes. The problem here is, your mayo can become too oily, too rich. (And the emulsion can break, but we're not floundering in that issue just now.)

With modernist thickeners such as xanthan and guar gum, these polymer molecules are way better at thickening than starch. Xanthan gum is a fantastic thickener when you use only a small amount, and it doesn't impede flavor or add unwanted carbs. Can you thicken gravy for chicken-fried steak using xanthan gum? Of course you can! These thickeners allow better control of viscosity, have greater thermal stability and don't contribute their own flavor, ureka!

A-ha Moment of the Week: Ketchup is an example of a product that is very thick at rest but liquifies with force (and you know this if you've banged on the bottle, only to have the contents shoot out). Via the process known as "shear thinning," at rest it's a fluid-gel hybrid where the gel is broken and some water can flow, but it's still thickened by polymers. It behaves like a solid but flows when force is applied. The ketchup actually undergoes a change in viscosity, wow.

What is a polymer, since I mention it? It's a long, flexible molecule made up of monomers, and can bend in any direction. OK, that's done.

Equations of the Week: n = nof(0) (where this o has a line through it and represents "phi.")
N is the viscosity of the solution, no is the viscosity of the pure continuous phase, f(phi) is a function that increases with phi.

(phi) = V dispersed, divided by V total where V dispersed is the volume occupied by non-solvent molecules and V total is the total volume of the solution. Just typing this in, I feel like the Scarecrow in the Wizard of Oz after he got his brain.

Next Week: Emulsions and Foams

Week 6: Heat Transfer, Harvard Style

Molten Chocolate Lava Cake from the Week 6 Lab, a tasty view of how heat moves from the outside to the inside.

The first note I wrote this week: Heat moves by random walk. Then I looked at the Harvard food science online review sheet, which begins differently: "Heat is transferred between molecules through random collisions, resulting in the diffusion of heat via random walks similar to those discussed previously." Er, right. I'm sure I wrote that somewhere.

Why not just say, "When heat moves, worlds collide?" Heat's effect on food is the reason someone invented the toaster oven, the waffle iron, the George Foreman grill, microwave, pressure cooker and sous-vide wand, you name it.

We're now halfway through the Harvard online course and diving into how heat moves through food. Time and temperature have always been an issue in my macarons class, because macarons crave precision. Bake at 325 degrees for exactly 13 minutes and nobody gets hurt. Under or over, and we've got a tray of head for the back door. 

When I worked the ovens at the gourmet-to-go shop Eatzi's, I shoved volumes of dough into ovens that ranged from hot to hotter and could eyeball how many more or less minutes were needed for a happy ending. Some chefs I know set their ovens at 400 and just bake everything at that temperature because it's easy to remember. How heat moves from the outside into the food, and for how long, is the stuff of Thanksgiving nightmares as you think of Chevy Chase carving into a deliciously golden brown bird in the film "Christmas Vacation" and it collapses.

A cool way to learn about heat transfer is with chocolate - what couldn't we learn from chocolate? There's a lab involving a molten chocolate lava cake, it's delicious and I wrote about the method - using a hot water bath to cook the cake just so, instead of blasting it in a hot oven and hoping for the best.

Now here's where I carved a star on my notes page. I'd written: "In order to properly cook something, it's not enough to cook inside to a target temperature (such as 165 for that Christmas turkey). The outside has another target, and it's much higher - higher than the boiling point of water. And the inside target is much below the boiling point of water. You have to try to achieve both heating protocals at the same time."

From here, we delved into browning reactions - and it makes sense. I've had guests ask in the croissants class why the croissant isn't golden brown and crunchy on the inside like it is on the outside. The previous paragraph tells you - the outside of the croissant browns because it exceeds a temp above the boiling point of water, while the inside stays soft because it remains below the boiling point. A-ha!

Remember how Julia Child told us to dry the meat before trying to brown it? That's because it wouldn't brown if it was wet. For browning to occur, water on the edge of the steak must evaporate and the external temperature has to reach the boiling point of water for the browning reaction known as Maillard to occur.

To learn more about browning as a factor of heat transfer, we also get a terrific lesson in french fries. Read on. But first, here comes you know what.

Equation of the Week: L = the square root of 4DT where D is the diffusion constant and T is the time (left over from last week but still good). With it, you can estimate cooking time for a particular food.

A-ha Lesson of the Week: The path to perfect french fries. Throw potatoes into room temp oil, then turn up the heat. This mimics the process of boiling water and allows heat to diffuse through the inside without burning the outside. Traditionally, potatoes are fried twice - once at a lower temp to cook the interior, and then again at a high temp to brown and crisp the outside. As Dan Souza of America's Test Kitchen explains, by going with room temp oil and raising the heat, the potatoes cook in one step, not two. As the oil warms, the interior cooks through and water begins to escape from the potato, just as it would in the traditional first fry. As the oil continues to heat, the fries begin to crisp and brown. This part of the process mimics the second high-heat fry, Souza says. Instead of tossing fries in the hot oil and retrieving them twice, just start with cool oil and remove the fries once when they're done.

Try this at home: Fry those potatoes. Dan likes to use Yukon Golds, less starchy than russets. Cut the potatoes into sticks. Dan chooses peanut oil, which produces light and crispy fried foods, he says. Use about 6 cups of room temp oil. Add potatoes and turn heat to high. Cook for about 5 minutes. The oil will mimic boiling water, so let the fries cook until they begin to firm, about 15 minutes. Don't stir. Don't panic. These beauties are soft at this point and easily broken. After the 15 minutes, go ahead with tongs and gently stir the fries around. Give them about 5 or 10 more minutes until golden crisp. Using a wire skimmer, remove to a wire rack. While still hot, season with kosher salt.

Delicious, this science!

Next week: Viscosity and Polymers