If you have Bake-Even strips, wet them and wrap them around the pan. If not, the cake should be baked in a water bath (a pan with about 1-1/2 inches of hot water) so the edges don’t dry out. If you’re using a water bath, wrap the springform pan in two layers of aluminum foil so no water will seep in while the cake bakes.
For the cake:
While the chocolate finishes melting, place the room-temperature egg whites in a large, grease-free mixing bowl with about a third of the sugar. Using an electric mixer, start beating on slow speed, gradually increasing the speed. Beat until the whites begin to look fluffy.
Then whisk in the egg yolks. Using a wire whisk, fold half of the meringue into the chocolate mixture. Fold in the remaining meringue with a rubber spatula, being sure to mix in the heavier batter at the bottom of the bowl. Gently fold until no streaks remain.
Refrigerate the cake for 1 hour, then run a knife around the edge of the pan and invert the cake onto a serving plate. Remove the bottom of the pan and the parchment circle, and replace the ring from the springform around the cake; it will be the mold for the two mousses.
For the middle layer:
While the chocolate is melting, soften the gelatin in a small dish with the cool water. Once it has softened, heat it on low heat in the microwave, stirring to dissolve. When the gelatin mixture is completely free of lumps, stir it into the melted chocolate.
Check the chocolate mixture. It must be free of lumps and the temperature should be about 80 degrees F – warm enough to keep the chocolate from setting up, but not so hot the whipped cream melts when it’s whisked in.
For the top layer:
When it’s ready to serve, remove the ring by running a thin knife gently around the edge of the pan, then open the lock and lift it off. Slice the cake with a warm, wet knife, wiping it off between slices; this will ensure a pretty presentation. Garnish with chocolate shavings or curls, chocolate sauce, or fruit. Yields about 16 servings.
For the cake: