Mash two bananas with a fork or mix finely with a hand blender.
Melt 30 grams of butter. Mix with the mashed bananas and sugar until frothy. Then stir in milk, flour and eggs. Now fold in baking powder, vanilla sugar, salt and grated hazelnuts.
Cut a banana into slices and carefully fold it into the batter. Pour the dough into a greased loaf pan. Bake at 180 ° C for a good one and a half hours. Then let the cake cool, turn it out on a kitchen rack and dust with powdered sugar.