Separate eggs. Mix egg yolks, sugar and vanilla sugar until frothy. Stir in the hazelnuts. If the dough is now too heavy, liquefy it with a little milk if necessary. Beat egg whites until stiff and fold in. Add baking powder.
Grease a loaf pan with fat and sprinkle with breadcrumbs. Pour in the dough and smooth it out.
Bake at 175 degrees in a preheated oven for about 60 minutes. Dust with powdered sugar if desired.