For the chocolate-nut cake, beat the room-warm butter with the sugar and vanilla sugar until white and fluffy. Mix in the egg yolks one at a time.
Now first stir in the grated walnuts and then the grated chocolate. Mix in the grated apples very briefly, on low speed. Sift the flour into a bowl with the starch and baking powder.
If cinnamon is desired, it can be added at this step. Now you need to stir the dry ingredients into the apple mixture.
Beat the egg whites until firm and gently fold into the apple mixture with a dough scraper.
Grease a cake pan well with butter and dust with flour. Fill the dough evenly into the cake pan and bake the cake at 160 °C-170 °C top and bottom heat for approx. 60 minutes.
Let the cake cool briefly in the pan and then carefully turn it out and let it cool. Dust with powdered sugar before serving.