Put the flour and cornstarch in a bowl and mix with baking powder. Put the eggs in another bowl and beat lightly. Add sugar, salt, butter and vanilla sugar and stir well. Add the sour cream. Stir in the flour. Finally fold in the cranberries and chocolate chips. Pour the batter into the mold.
Bake in the preheated oven on the middle rack for approx. 20-25 minutes until golden brown.
Beat the icing sugar with a little cranberry juice until smooth and coat the muffins with it.