For the banana muffins, melt the butter and let it cool down a bit. Mix the flour with the baking powder, salt, cinnamon, sugar and vanilla sugar.
Mix the eggs with the butter and milk. Peel the bananas and mash them finely with a fork. Then stir everything in well until a smooth batter is formed.
Pour the batter into the muffin cups. Place a walnut in the center and bake the banana muffins in the oven at 180 °C for about 25 minutes until golden brown.