I found this recipe at America’s Test Kitchen. I had been searching for a good mousse cake recipe but have not had much luck. This is the first recipe I found that tastes great and has the perfect mousse texture, so light and perfectly sweet. I love it!
To make this cake you will need a 9 inch spring form pan that is 3 inches deep.
6 tablespoon unsalted butter, cut into small pieces
7 ounce bittersweet chocolate, chopped fine
3/4 teaspoon instant espresso powder
4 large eggs, separated
1 1/2 teaspoon vanilla extract
1/8 teaspoon cream of tartar
1/8 teaspoon salt
1/2 cup packed (2 1/3 ounces) light brown sugar
5 tablespoons hot water
2 tablespoons cocoa power
7 ounces semisweet chocolate, chopped fine
1 1/2 cups heavy cream, chilled
1 tablespoon granulated sugar
1/8 teaspoon salt
White Chocolate Mousse
1 teaspoon unflavored gelatin
1 tablespoon water
6 ounces white chocolate, chopped fine
1 1/2 cup heavy cream, chilled
Shaved chocolate ( optional )
Adjust oven rack to middle position and heat oven to 325 degrees.
Grease a 9 inch springform pan and set aside.
Melt butter, chocolate, and espresso powder in large heatproof bowl set over saucepan filled with 1 inch barely simmering water, making sure that water does not touch bottom of bowl; stir occasionally until smooth. Remove from heat and let cool slightly, about 5 minutes. Whisk in egg yolks and vanilla; set aside.
Using stand mixer fitted with whisk, whip egg whites, cream of tartar, and salt on medium-low speed until foamy, about 2 minutes. Add half of sugar and whip until combined, about 15 seconds. Add remaining sugar, increase speed to high, and whip until soft peaks form, about 2 minutes longer, scraping down bowl halfway through whipping. Using hand whisk. Fold one-third beaten egg whites into chocolate mixture to lighten. Using rubber spatula, fold in remaining egg whites until no white steaks remain. Pour the batter to prepared pan and smooth top with rubber spatula.
Bake until cake is risen, firm around edges, and center spring back when pressed gently with finger, 15-19 minutes, rotating pan halfway through baking. Let cake cool completely in pan on a wire rack. ( Cake will collapse as it cools.) Loosen sides from pan with a knife.
Combine hot water and cocoa in small bowl; set aside. Melt chocolate in large heatproof bowl set over saucepan filled with 1 inch barely simmering water, making sure that water does not touch bottom of bowl; stir occasionally until smooth. Remove from the heat and let it cool slightly, 2 to 5 minutes.
Using stand mixer fitted with whisk, whip cream, sugar, and salt on medium-low speed until foamy, about 1 minutes. Increase speed to high and whip until soft peaks form, 1 to 2 minutes.
Whisk cocoa mixture into melted chocolate until smooth. Using hand whisk, fold one-third of whipped cream into chocolate mixture to lighten. Using rubber spatula, fold in remaining whipped cream until no white streaks remain. Pour the mousse into pan over cooled cake, smooth top with offset spatula, and gently tap pan on counter to release air bubbles. Wipe inside edge of pan with damp cloth to remove any drips. Refrigerate cake for 30 minutes.
White Chocolate Mousse
While waiting for chocolate mousse to set; start making the top layer.
Sprinkle gelatin over water in small bowl and let sit until gelatin softens, about 5 minutes. Place chocolate chips in medium heatproof bowl and set aside. Add 1/2 cup of heavy cream into saucepan and bring it to simmer over medium-high heat. Remove from heat, add gelatin mixture, and stir until fully dissolved. Pour cream mixture over chocolate chips and let it sit, covered, for 5 minutes. Whisk mixture gently until smooth. Let cool completely, stirring occasionally ( mixture will thicken slightly).
Using stand mixer fitted with whisk, whip remaining 1 cup cream on medium-low speed until foamy, about 1 minute. Increase speed to high and whip until soft peaks form, 1 to 2 minutes. Using hand whisk, fold one-third of whipped cream into white chocolate mixture to lighten. Using rubber spatula, fold in remaining whipped cream until no white streaks remain. Slowly pour white chocolate mousse into pan over middle layer and smooth top with offset spatula. Return cake to refrigerator and chill until set, at least 3 hours or overnight.
Run thin knife around pan to loosen cake or use a hairdryer to slightly heat the sides of the pan; remove side of pan. Garnish top of cake with shaved chocolate.
Recipe adapted from : America’s Test Kitchen Special Collection’s Edition