Soak the apples, diced, in ruhm for about 30 minutes.
Mix the butter with sugar and eggs, add powdered hazelnuts little by little, cocoa, cinnamon, flour mixed with baking powder. Stir in diced apples.
Pour the mixture in a baking tin, buttered and floured, and bake for about one hour at 170°

(Principe is the real name of a very skilled pastry cook in Milan. If you like, you can line the baking tin with short pastry. I tried this cake in both ways and it tastes wonderful.)