Running wild on a suggestion that I might learn something in the Harvard online course Science and Cooking: From Haute Cuisine to Soft Matter Science, I took the plunge. Let's save a discussion of how it's going for another post. Just know this: There's chocolate about halfway through the 10-week course. This is a soothing reward for all the physics and math you'll go through (and forgot the moment you took the SAT).
Molten Chocolate Lava Cake started out as a goof when a chef underbaked it and served it anyway. This launched a taste for firmness on the outside and gooey richness on the inside. Trouble is, many of us manage to bake the cake all the way through - as a cake should be - and that disappoints the guests, who want to slice in and release the lava. These cakes are often baked in small ramekins and placed in a 350-degree oven for some mysterious amount of time that nobody understands (remember, it was a MISTAKE when it first happened). The cakes are removed from the ramekins presumably set, inverted and whacked with whipped cream, ice cream, fresh raspberries, what have you.
I've taught the recipe before for Sur La Table and blanched at the results - fully cooked through in under 8 minutes, merde. Imagine my glee in getting this cake as a lab assignment in which we take the cake's temperature at 3-minute intervals to learn about how heat transfers, or diffuses, through the batter. In the above image, notice how the slice taken at the blue pansy is baked solid through at 30 minutes. The slice at the bottom was at 18 minutes; the 15-minute slice could not be sliced, it was so gooey. See the slice in the middle, just left of the pansy? That's perfection at 21 minutes.
Here's how to hit that mark. Use a hot water bath, just as you would for creme brulee or other custards where you want to slow down the outside cooking to give heat time to diffuse inward. In a boiling water bath, the temperature around the cake batter is 212 instead of 350 like the oven. This gives you much more control and more time to achieve what you want - a set exterior and a gooey interior. Do it like this, from the Harvard class.
Molten Chocolate Lava Cake
120g dark chocolate, chopped
8 Tbsp butter
(107g)
120g sugar
5 large eggs (275g)
60g flour
0.5g salt (pinch)
Preheat oven to 350F. Boil some water for adding to a baking pan large enough to hold 6 ramekins 4 ounces in size.
Melt chocolate chips and butter in a small pot on low heat, stirring, until melted. Allow to cool slightly. In a separate medium bowl, whisk sugar and eggs together. Slowly whisk in chocolate mixture.
In another bowl, place flour and salt, stir to combine, then mix into the wet ingredients. Whisk a bit to remove any flour clumps.
Place the ramekins in a
baking dish and pour batter evenly across each ramekin (at least 1 inch high).
Pour boiling water around the cups until about 1/2-inch deep, being careful not to
splash any into the ramekins.
Bake. At 21-24 minutes you should still have a molten center but a
good baked cake around it.
I ate the rest of the test results. End of story.
