Place the mixing bowl in a bowl with warm water (butter is easier to stir). Put the butter and sugar in the bowl and stir with the hand mixer until the mixture is creamy. Stir in eggs, yogurt and vanilla sugar. Add flour with baking powder and salt. Add milk, stirring constantly, until a thick paste has formed.
Preheat the waffle iron. Brush the hot waffle iron with a little oil (I prefer rapeseed oil) and bake the waffle.
Then sprinkle the arms with powdered sugar or serve with ice cream and hot fruits.