How to make
Crush the biscuits in a bowl, add the vanilla sugar and finally the melted butter. Mix everything well and place the mixture in cake tin with a removable bottom, by pressing it with a spoon, until an even cake layer obtained. The cake tin with the cake layer is placed in the refrigerator to stand for at least 1 hour, so that it can set.
Melt the chocolate, which has been broken into pieces in advance, in a suitable container in a water bath. Gradually add the liquid cream, which is preheated. The two ingredients are mixed, until a homogeneous mixture is obtained.
The eggs are divided into two separate bowls of egg whites and yolks, by being careful not to get the yolk in the egg white. Add the yolks to the chocolate with the liquid cream and mix vigorously, until a homogeneous mixture is obtained.
Beat the egg whites into a frothy mixture with a mixer, gradually add the sugar, so that it can melt. The egg whites are added to the chocolate mixture in three potions and the mixture is beaten with a stirrer with vigorous hand movements. The chocolate mousse must be homogeneous, without white spots of egg whites.
Remove the cake tin with the cake layer from the refrigerator and pour the mousse in it. Smooth it out well and place the cake tin in the refrigerator for a few hours. It's best to leave the special chocolate cake overnight.
Before serving, decorate the chocolate mousse cake with waffle balls or other suitable chocolate decoration.
