Classic Chocolate Mousse Cake

👨‍🍳 Method

For the Cake

1. 1
   Preheat the oven to 170°C (340°F) and grease a round pan 22 cm across.

   ⚙ Preheating the OvenOven

   💡Put things in the oven only once it's reached temperature, after the heating light has gone off: an oven that hasn't reached temperature changes baking times, and the bake burns outside or stays underbaked.
2. 2
   Melt the chocolate and butter in a double boiler and let cool slightly.

   Double boiler (bain-marie)orMicrowave

   💡In the microwave, melt in short bursts, stirring in between, until the chocolate and butter are smooth and liquid.
3. 3
   Add the sugar to the chocolate and stir until it dissolves, then add the eggs one at a time, stirring constantly, followed by the vanilla.
4. 4
   Sift the flour and cocoa over the top, add the salt and Fold gently, just until the batter is smooth.

   ⚙ FoldingSilicone spatulaSifter

   💡Fold with a spatula, in broad strokes from the bottom up, and stop when there are no streaks: vigorous mixing knocks the air out of the foam. Add whipped mixtures in stages: a quarter first, to lighten the mixture.

   💡Fold with a spatula, in broad strokes from the bottom up, and stop when there's no dry flour: vigorous mixing of a batter with flour develops gluten.
5. 5
   Pour into the pan.

   Round pan
6. 6
   Bake 25 minutes, until a toothpick inserted in the center comes out with moist crumbs.

   ⚙ BakingOvenRound pan

   💡Check by the cue (until…), not just the clock: every oven bakes a little differently.
7. 7
   Let the cake cool completely.

To assemble

1. 8
   Melt the chocolate in a double boiler, stirring, and let it cool slightly.

   Double boiler (bain-marie)
2. 9
   Whip the cold cream with the powdered sugar and vanilla to stiff peaks.

   ⚙ WhippingBowlHand mixerorStand mixerorWhisk

   💡Whip cream very cold, in a chilled bowl with chilled beaters, and stop when it holds firm: overwhipping turns it grainy and buttery.
3. 10
   Fold the melted chocolate into the whipped cream gently, until the mousse is even.

   ⚙ FoldingSilicone spatula
4. 11
   Pour the mousse over the cold cake and smooth the top.

   Offset spatula
5. 12
   Refrigerate at least 4 hours, until the mousse sets.

   Refrigerator