French Chocolate Mousse Cake

Instructions

1. Prepare the cake base
   Preheat the oven to 350°F (175°C). Grease and line a 9-inch (23cm) springform pan with parchment paper. Melt 150g of the dark chocolate with 100g of butter in a heatproof bowl set over a pan of simmering water. Stir until smooth, then remove from heat and let cool slightly.
2. Mix the cake batter
   In a large bowl, beat the egg yolks with 100g of granulated sugar until pale and thick. Fold in the melted chocolate mixture. Gently fold in the sifted flour and salt until just combined. In a separate bowl, whisk the egg whites until soft peaks form, then gradually add the remaining 50g of sugar, beating until stiff and glossy. Carefully fold the egg whites into the chocolate mixture in three additions.
3. Bake the cake
   Pour the batter into the prepared pan and smooth the top. Bake for 25-30 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs. Allow to cool in the pan for 10 minutes, then remove the sides of the springform pan and let cool completely on a wire rack.
4. Prepare the chocolate mousse
   Melt the remaining 50g of dark chocolate and let cool slightly. In a large bowl, beat the mascarpone cheese with the confectioners' sugar and vanilla until smooth. In another bowl, whip 200ml of the heavy cream until stiff peaks form. Fold the melted chocolate into the mascarpone mixture, then gently fold in the whipped cream until well combined.
5. Assemble the cake
   Once the cake is completely cool, slice it horizontally into two even layers. Place the bottom layer on a serving plate. Spread the chocolate mousse evenly over the bottom layer, reserving about 1/4 cup for decoration if desired. Place the top layer of cake over the mousse.
6. Prepare the ganache topping
   In a small saucepan, heat the remaining 100ml of heavy cream until it just begins to simmer. Pour over the melted milk chocolate and let stand for 1 minute, then stir until smooth. Let cool slightly until it thickens a bit but is still pourable. Pour the ganache over the top of the cake, allowing it to drip slightly down the sides.
7. Decorate and chill
   If you reserved some mousse, transfer it to a piping bag fitted with a star tip and pipe decorative rosettes around the edge of the cake. Dust the top lightly with cocoa powder. Refrigerate the cake for at least 3 hours or overnight to set the mousse completely.