Triple Chocolate Mousse Cake Recipe

Prepare pan

Preheat oven to 350°F (175°C). Butter and line the bottom of a 9-inch (23 cm) springform pan with parchment paper; lightly butter parchment.

Make sponge batter

Whisk together flour and cocoa powder; set aside. In a bowl, whisk egg yolks with 3 tablespoons sugar until pale and slightly thickened. In a separate clean bowl, beat 3 egg whites to soft peaks, then gradually add a tablespoon of sugar and continue to beat to glossy stiff peaks.

Combine and bake

Fold the yolk mixture gently into the beaten whites, then fold in the flour/cocoa mixture in two additions, keeping as much air as possible. Spoon batter into prepared pan and smooth top. Bake 10–12 minutes or until springy and a toothpick comes out clean. Cool in pan on rack for 5 minutes, then remove outer ring and cool completely on rack. Once cooled, if the sponge domed, trim to an even 9-inch circle. Return to springform base for assembly.

Melt chocolate

Place 8 oz chopped dark chocolate and 2 tbs butter in a heatproof bowl set over barely simmering water (double boiler) or microwave in 20-second bursts, stirring between, until smooth. Remove from heat and let cool slightly.

Temper yolks

In a small saucepan, gently heat 1 cup heavy cream until steaming but not boiling. In a bowl, whisk 4 egg yolks with 2 tbs sugar until combined. Slowly pour one-third of the hot cream into the yolks, whisking constantly to temper. Then return tempered yolks into the remaining hot cream in the saucepan and cook over low heat, stirring constantly, until the mixture thickens slightly and coats the back of a spoon (do not boil). Remove from heat and cool slightly.

Finish mousse

Pour the warm custard over the melted dark chocolate and stir until fully incorporated and glossy. Stir in 1 tsp vanilla and a pinch of salt. When the mixture cools to lukewarm (room temperature), whip 1 cup heavy cream to soft-medium peaks and fold one-third into the chocolate to loosen, then fold in remaining whipped cream gently until homogeneous. Chill slightly (10–15 minutes) if needed so it holds shape for layering.

Bloom gelatin and melt chocolate

Sprinkle 1 tsp gelatin over 2 tbs cold water in a small bowl and let bloom 5 minutes. Heat 1 cup whole milk with 1 tbs sugar until just steaming. Place 6 oz chopped milk chocolate in a bowl; pour the hot milk over chocolate, let sit 1 minute, then stir until smooth. Microwave the bloomed gelatin 10–15 seconds or heat gently until liquefied, then whisk into the warm milk-chocolate mixture until fully incorporated. Let cool to room temperature but not set.

Fold in cream

Whip 1 cup heavy cream to soft peaks. Fold one-third of the whipped cream into the cooled milk-chocolate base to lighten, then gently fold in the remaining cream until smooth and airy. Chill briefly (10 minutes) if needed before layering.

Melt white chocolate

Place 6 oz chopped white chocolate and 1 tbs heavy cream in a heatproof bowl and melt gently over a double boiler or in short microwave bursts until smooth. Remove from heat and let cool to lukewarm.

Make Italian-style meringue

In a small saucepan, combine 2 tbs sugar with 2 tbs water and bring to a boil until the syrup reaches about 238–240°F (114–116°C) (soft-ball stage). While syrup heats, begin whipping 3 egg whites with 1 tsp lemon juice to soft peaks. With the mixer running, slowly pour the hot sugar syrup into the whites in a thin steady stream and continue beating until the meringue is glossy and cooled to room temperature.

Combine with white chocolate and cream

Fold a quarter of the meringue into the melted white chocolate to loosen it, then fold in the remaining meringue gently until well combined. Fold in 1 cup whipped cream (soft peaks) in two additions until smooth and airy. Chill briefly if necessary to set slightly before assembly.

Layer mousses

Place the cooled sponge base back in the springform ring (if removed). If you prefer a thinner base or crust, you can use a cookie crumb crust — this recipe uses the sponge. Spread an even layer of the dark chocolate mousse (about one third of the total dark mousse) on the sponge, smoothing the top with an offset spatula. Chill the pan for 10–15 minutes to set the layer slightly (this prevents mixing).

Next, gently spread the milk chocolate mousse over the chilled dark layer, smoothing the surface. Return to the refrigerator for another 10–15 minutes to slightly set. Finally, spread the white chocolate mousse over the milk layer and smooth the top. Tap the pan lightly on the counter to remove air pockets and ensure even layers.

Cover the assembled cake with plastic wrap and refrigerate at least 4 hours, preferably overnight, to fully set the mousses. For firmer slices, chill 6–8 hours.

Unmold and decorate

Run a thin knife around the inside edge of the springform and release the ring. Transfer cake to a serving plate. Dust the top lightly with 1 tsp cocoa powder, sprinkle chocolate shavings or curls, and arrange fresh berries if using.

Slice

For clean slices, dip a long sharp knife in hot water, wipe dry, then slice. Wipe the knife between cuts. Serve chilled.