Bittersweet Chocolate Mousse Cake

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.