Adapted from “The Cake Bible,” by Rose Levy Beranbaum. Makes 1 cake.
Ingredients
1 pound bittersweet chocolate
1 cup unsalted butter
6 large eggs
Directions
Preheat oven to 425 degrees.
Prepare the baking pan: Butter and line one 8-inch springform with buttered parchment or wax paper, then wrap outside of pan with heavy duty foil. (Later, you’ll be placing it inside a large roasting pan half-filled with water. Stay tuned.)
In a large metal bowl set over a pan of hot, not simmering water (the bottom of the bowl should not touch the water) combine the chocolate and butter and let stand, stirring occasionally, until smooth and melted. (The mixture can be melted in the microwave on high power, stirring every 15 seconds. Remove when there are still a few lumps in the chocolate and stir until fully melted.)
For stand mixer: In the bowl of a stand mixer set over a pan of simmering water, heat eggs, stirring constantly to prevent curdling, until just warm to the touch. Remove from heat and beat, using whisk attachment, until triple in volume and soft peaks form, about 5 minutes.
For hand mixer or manually with a whisk: To ensure maximum volume, beat the eggs over simmering water until they are hot to the touch, about 5 minutes. Remove from heat and beat until cool.
Using a large wire whisk or rubber spatula, fold half the eggs into the chocolate mixture until almost incorporated. Fold in the remaining eggs until just blended and no streaks remain. Finish by using a rubber spatula to ensure that the heavier mixture at the bottom is incorporated. Scrape into prepared springform pan and smooth with the spatula. Set pan in the larger roasting pan and surround it with 1 inch very hot water. Bake 5 minutes. Cover loosely with a piece of buttered foil and bake 10 minutes. (The cake will look soft, but this is as it should be.)
Let cake cool on a rack 45 minutes. Cover with plastic wrap and refrigerate until very firm, about 3 hours.
To unmold: Have ready a serving plate and a flat plate at least 8 inches in diameter, covered with plastic wrap. Wrap sides of pan with a hot, damp towel.
Run a thin metal spatula around the sides of the cake and release the sides of the springform pan. Place the plastic-wrapped plate on top and invert. Wipe bottom of the pan with a hot, damp towel. Remove bottom of pan and parchment. Reinvert onto serving plate.
Use a stencil to decorate with powdered sugar.
