Triple Chocolate Mousse Cake Recipe

Prepare and bake

Preheat the oven to 350°F (175°C). Grease and line the bottom of an 8-inch (20cm) springform pan with parchment and lightly butter the sides. In a medium bowl whisk together flour, cocoa powder, baking powder, baking soda and salt until uniform.

In a separate large bowl, whisk the eggs and granulated sugar until combined, then add milk, oil and vanilla and whisk until smooth. Gradually fold the dry ingredients into the wet until just combined — do not overmix.

Stir in the hot water slowly to loosen batter; the batter will be thin. Pour into the prepared pan and bake 20–25 minutes or until a toothpick inserted in the center comes out with a few moist crumbs. Cool completely in the pan on a wire rack.

Once cooled, level the cake top if necessary. If the cake domed, trim to make a flat surface. Leave the cake in the springform pan to build mousse layers on top (you can remove collar briefly to line sides with acetate if desired).

Make chocolate base

Chop the bittersweet chocolate finely and place in a heatproof bowl. Heat 1 cup heavy cream over medium heat until it just begins to simmer; remove from heat and pour about one-third over the chocolate. Let sit 1 minute, then whisk until smooth. Add the butter and whisk to glossy consistency.

In a small bowl whisk the egg yolks with 2 tablespoons sugar until slightly paler. Temper the yolks by whisking in 2–3 tablespoons of the warm chocolate mixture, then pour the tempered yolks back into the remaining warm chocolate while whisking constantly. If worried about raw eggs, you can cook the yolk mixture over a double boiler to 160°F (71°C) before combining, stirring constantly.

Whip remaining heavy cream (if any left from the recipe balance; if using exactly amounts given, cool the chocolate mixture to room temp then whip 1/2 cup additional cream to soft peaks and fold in) to medium-soft peaks and fold gently into the cooled chocolate base until homogeneous. Smooth the mousse over the cooled cake to form an even bottom mousse layer about 3/8–1/2 inch thick. Refrigerate 20–30 minutes to set slightly.

Bloom gelatin

If using powdered gelatin, combine 2 tablespoons cold water with 1 tablespoon powdered gelatin and let bloom 5 minutes. If using gelatin sheet, soak sheet in cold water 5–7 minutes, then squeeze out excess before use.

Chop milk chocolate and place in a bowl. Heat about 1/3 cup heavy cream until steaming (not boiling) and pour over milk chocolate; let sit 1 minute, then whisk until smooth. Stir in 1 tablespoon sugar.

If using gelatin powder: warm the bloomed gelatin briefly (10–15 seconds) in the microwave or in a small saucepan until melted but not boiling, then whisk into the warm milk chocolate mixture. If using a sheet, melt the squeezed sheet in a small amount of warm cream and add to chocolate. Allow mixture to cool to lukewarm.

Whip remaining heavy cream to soft peaks and fold one-third into the chocolate to lighten, then fold in the rest gently until uniform. Pour the milk-chocolate mousse over the set dark-chocolate layer, smoothing the top. Chill 30–40 minutes until the middle layer is slightly firm.

Prepare gelatin and chocolate

Bloom gelatin (same as for milk chocolate): combine 2 tablespoons cold water with 1 tablespoon powdered gelatin or soak one sheet. Chop white chocolate and place in a bowl. Heat about 1/3 cup heavy cream until steaming and pour over white chocolate; let sit 1 minute then whisk until smooth. Stir in vanilla.

Melt the bloomed gelatin gently and whisk into the warm white chocolate mixture. Allow the mixture to cool to lukewarm but still pourable.

Whip the remaining cream to soft peaks and fold a small portion into the white chocolate to lighten, then fold in the rest gently until smooth and airy. Pour carefully over the chilled milk-chocolate layer and smooth the top. Refrigerate the cake at least 4 hours, preferably overnight, to fully set.

Unmold and finish

Run a thin knife around the springform edge to loosen. Remove the outer ring; if you used acetate, peel it away gently. Dust the top or sides lightly with sifted cocoa powder if desired. Sprinkle chocolate shavings or curls over the top and arrange fresh berries around the edge or on top for color.

Slice with a hot, dry knife (dip in hot water and wipe dry between slices) for clean layers. Store any leftovers covered in the refrigerator for up to 3 days.