For the banana coconut muffins, beat the eggs with the powdered sugar and vanilla sugar until very foamy. Gradually stir in butter and milk. Add 1-2 tablespoons of Nutella to the batter.
Mix the remaining ingredients (except banana cubes) and stir into the liquid mixture. Finally, carefully fold in the banana cubes.
Pour the batter into prepared muffin tins and bake in the preheated oven at about 180 degrees for about 20 minutes.