1. Separate the egg whites from the yolks.
2. Mix the yolks with brown sugar and vanilla sugar.
3. Add the mascarpone and whisk together.
4. Beat the egg whites until stiff peaks form, then gently fold them into the previous mixture using a spatula. Set aside.
5. Dip the biscuits quickly in coffee before lining the bottom of the dish with them.
6. Cover with a layer of mascarpone cream, then repeat the process by alternating layers of biscuits and cream, finishing with a layer of cream.
7. Sprinkle with cocoa powder.
8. Refrigerate for a minimum of 4 hours, then serve chilled.