Chocolate Mousse Cake Recipe

Melt chocolate and butter

Place chopped bittersweet chocolate and butter in a heatproof bowl set over a simmering pot of water (double boiler) or microwave in 20–30 second bursts, stirring until smooth. Remove from heat and let cool slightly (5 minutes).

Warm cream

Heat heavy cream in a small saucepan until just simmering (do not boil). Pour about one-third of the hot cream into the melted chocolate and stir to create a smooth ganache; gradually stir in the remaining cream until fully incorporated. Stir in vanilla extract and a pinch of salt. Set aside to cool to lukewarm.

Prepare egg yolks

Whisk the 5 egg yolks lightly in a bowl. Temper the yolks by whisking a few tablespoons of the warm chocolate mixture into the yolks to raise their temperature, then slowly whisk the yolk mixture back into the main chocolate mixture until smooth. (This avoids scrambling the yolks.)

Whip egg whites

In a clean, dry bowl, beat the 5 egg whites with an electric mixer until foamy. Gradually add 90 g granulated sugar and continue to beat until medium–stiff glossy peaks form.

Fold to make mousse

Fold one-third of the whipped egg whites into the chocolate mixture gently to lighten it, then fold in the remaining whites in two additions until no streaks remain, being careful not to deflate the mixture. Pour the mousse into an 8–9 inch (20–23 cm) springform pan or ring lined with parchment, smoothing the top.

Chill

Refrigerate the mousse for at least 4 hours or until set (overnight preferred). If using a sponge base, see the optional sponge directions and place sponge in pan before pouring mousse.

Preheat oven to 180°C (350°F). Line a small baking sheet or cake pan with parchment. Whisk together flour, cocoa powder and 30 g sugar. In a separate bowl beat 1 egg with 10 ml vegetable oil until blended, fold into dry ingredients to form a thin batter. Spread batter in an even thin layer (about 1/4 inch) and bake 6–8 minutes until just set. Cool, trim to fit springform pan base and place in pan before pouring mousse. This gives a thin textured base; if omitted, mousse is fine on its own.

Make Italian meringue

Combine 200 g granulated sugar with 60 ml water in a small saucepan and bring to a boil without stirring until sugar syrup reaches 115°C–120°C (240°F–248°F, soft-ball stage) on a candy thermometer. Meanwhile, start whipping the 4 egg whites with 1 tsp cream of tartar to soft peaks. When syrup reaches temperature, slowly pour the hot syrup in a thin stream into the whipped whites while continuing to beat on medium-high speed. Beat until the bowl is cool and glossy stiff peaks form, then beat in 1 tsp vanilla extract.

Top the chilled mousse

Remove the chilled mousse from the refrigerator. Pipe or spread the Italian meringue over the mousse, creating peaks or swirls with a spatula.

Toast meringue

Use a kitchen blowtorch to evenly toast the meringue until golden brown. If you don't have a torch, place the cake under a hot broiler for 1–2 minutes, watching carefully to avoid burning.

After toasting, chill the cake briefly (10–15 minutes) to stabilize the meringue. Release and remove the springform ring and transfer cake to a serving plate if desired.

Dust the top lightly with 1 tsp unsweetened cocoa powder and scatter 30 g shaved chocolate or curls over the meringue.

Cut cake into 8 slices. Serve each slice with one scoop of vanilla ice cream. Optionally add extra chocolate shavings at the side.