Chocolate Mousse Cake Recipe

Prepare

Preheat oven to 350°F (175°C). Grease and line the bottom of a 9-inch (23 cm) round springform pan with parchment; grease sides.

Mix dry ingredients

In a medium bowl whisk together all-purpose flour, cocoa powder, baking powder, baking soda and salt until evenly combined.

Combine wet ingredients

In a separate bowl whisk eggs with granulated sugar until slightly pale. Add milk, vegetable oil and vanilla extract and whisk until smooth.

Make batter and bake

Add the dry ingredients to the wet and stir just until combined; do not overmix. Pour batter into prepared pan (about 1 inch thick). Bake 15–18 minutes or until a toothpick in the center comes out with a few moist crumbs. Remove and let cool in pan on a rack while preparing mousses. Leave in pan for assembly.

Temper yolks and sugar

Place the chopped dark chocolate in a heatproof bowl. In a small saucepan warm 1/2 cup heavy cream just until steaming. In a separate small bowl whisk the egg yolks with 2 tbs sugar until smooth. Slowly whisk about 1/4 cup of the hot cream into the yolks to temper, then pour the tempered yolk mixture back into the remaining hot cream and return to low heat, stirring constantly until mixture slightly thickens (do not boil). Immediately pour the hot custard over the chopped chocolate and let sit 1 minute.

Emulsify chocolate custard

Stir the chocolate and custard together until smooth and glossy. Add the softened butter and vanilla extract, stirring until incorporated. Let the chocolate mixture cool to room temperature (about 20–30 minutes), stirring occasionally to release heat.

Fold in whipped cream

Whip 1 cup heavy cream to soft peaks. Gently fold one-third of the whipped cream into the cooled chocolate base to loosen it, then fold in the remaining whipped cream in two additions until evenly combined and light. Do not overfold.

Layer mousse

Spoon or pipe the dark chocolate mousse over the cooled sponge in the springform pan, smoothing the top to an even layer about 3/4–1 inch thick. Refrigerate while you prepare the milk chocolate mousse, at least 20 minutes to set slightly.

Make milk chocolate custard

Place milk chocolate in a heatproof bowl. Warm 1/3 cup heavy cream until steaming. In a small bowl whisk egg yolks with 1 tbs sugar. Temper the yolks by adding about 2 tablespoons hot cream, then combine back into the saucepan and heat gently until slightly thickened. Pour hot custard over the chopped milk chocolate and let sit 1 minute.

Emulsify and cool

Stir until smooth and add the 1/2 tbs softened butter and vanilla extract. Allow the milk chocolate mixture to cool to room temperature (15–20 minutes).

Fold in whipped cream

Whip 3/4 cup heavy cream to soft peaks. Fold one-third into the cooled milk chocolate base to loosen, then fold in remaining whipped cream until homogeneous and airy.

Layer top mousse

Gently spread or pipe the milk chocolate mousse over the set dark mousse to an even layer about 3/4 inch thick. Smooth the top with an offset spatula. Chill in refrigerator at least 1 hour to firm both mousse layers before glazing.

Prepare glaze

Place chopped milk chocolate and butter in a heatproof bowl. In a small saucepan heat 1/2 cup heavy cream until simmering (do not boil). Pour the hot cream over the chopped chocolate and butter and let sit 1 minute, then stir until smooth and glossy.

Cool slightly

Allow the glaze to cool until thickened but still pourable (roughly 5–10 minutes). It should hold a little shape on the back of a spoon; if it’s too thin it will soak into the mousse.

Glaze the cake

Remove the chilled cake from the refrigerator. Loosen the springform and place the pan on a rack with parchment underneath to catch drips. Pour the glaze gently over the center of the cake, using an offset spatula to nudge it to the edges so it forms a smooth, solid milk chocolate top. Work quickly before the glaze sets. If needed, smooth the edge with a warm offset spatula for a clean finish.

Chill to set

Return the cake to the refrigerator and chill at least 1 hour, until the glaze is fully set and the mousse layers are firm.

Final unmolding

Once the glaze is set, run a thin knife around the springform ring to loosen any adhesion. Release the ring and transfer the cake to a serving plate.

Garnish and serve

Optionally dust the cake edge lightly with cocoa powder and sprinkle a few sea salt flakes on top of the glaze for contrast. Slice with a hot, clean knife (dip in hot water and wipe dry between cuts) to get clean slices.

Storage

Store covered in the refrigerator for up to 3 days. For best texture remove from fridge 15–20 minutes before serving.