Separate the eggs for the dough. Mix the egg yolks with the butter, sugar and vanilla sugar until frothy. Beat the egg whites with a pinch of salt until they are very stiff. Add the melted chocolate with nuts, baking powder and flour to the egg yolk mixture and mix well. Then fold in the two grated apples and the egg whites. Pour the batter into a greased bundt cake pan.
Bake in a preheated oven at 180 ° C for about 1 hour.