From America's Test Kitchen Season 4: Showstopper Desserts
When we first prepared a baked mousse cake recipe, it came out of the oven a dense, homely mess. But this ugly duckling showed promise. The flavor was excellent: fudgy, chocolaty, and rich. With a more mousselike texture and a bit of a facelift, this cake could be a winner.
We tackled the most important ingredient first: the chocolate. Hershey’s Special Dark made a great cake with nicely balanced chocolate flavor, but bittersweet chocolate alone didn’t bring the intensity we wanted. We found that adding a bit of unsweetened chocolate provided a deep, chocolaty taste and a darker, slightly more sophisticated quality.
The perfect amount of butter and egg yolks gave our cake its melt-in-your-mouth texture. A pinch of salt heightened the chocolate flavor, and vanilla played a dual role, rounding out the smokiness of the chocolate and taming the egginess of the yolks. The final ingredient was the beaten egg whites, which are traditionally folded into the batter just before it goes into the oven. But the delicate whites collapsed under the weight of the chocolate, resulting in a dense, bricklike texture. To make the whites sturdier, we added brown sugar to them. This produced a creamy meringue that held up well when folded into the chocolate mixture and produced a baked mousse cake that was moist, rich, and creamy.
Makes one 9-inch cake, serving 12 to 16
Because it is available in most supermarkets and has scored highly in past tastings, Hershey's Special Dark is the chocolate of choice in this recipe. Other bittersweet chocolates will work, but because amounts of sugar and cocoa butter differ from brand to brand, they will produce cakes with slightly different textures and flavors. When crumbling the brown sugar to remove lumps, make sure that your fingers are clean and grease-free; any residual fat from butter or chocolate might hinder the whipping of the whites. If you like, dust the cake with confectioners' sugar just before serving or top slices with a dollop of lightly sweetened whipped cream.