1. In a heatproof bowl, melt the dark chocolate over simmering water. Let it cool slightly.
2. In another bowl, whip 1 cup of heavy cream until soft peaks form. Fold in the melted dark chocolate.
3. In a separate bowl, beat the egg yolks with sugar until pale. Fold into the chocolate mixture.
4. In another bowl, whip the egg whites until stiff peaks form. Gently fold into the chocolate mixture.
5. Repeat the process for the milk chocolate and white chocolate layers.
6. Layer the dark chocolate mousse in a cake pan, followed by the milk chocolate, and then the white chocolate mousse.
7. Chill the cake in the refrigerator for at least 4 hours or overnight.
8. Before serving, whip the remaining heavy cream and spread it on top of the cake.

Discover my favorite kitchen tools I always use.