For the muffins, beat the butter, sugar, salt and vanilla sugar until frothy. Beat the eggs one by one. Mash the banana with a fork and stir in with the cream. Mix the flour with the baking powder and baking soda and stir into the dough.
Pour the dough into a greased muffin tin or paper cases and bake at 180 ° C (top / bottom heat) for 20 minutes. Allow to cool slightly.
For the frosting, melt the chocolate in a water bath and let it cool down. Meanwhile, dissolve the cocoa powder in the boiling water and stir into a paste. Stir the butter until it is soft and stir in the powdered sugar. Mix with the melted chocolate and cocoa paste.
Pour the frosting into a piping nozzle and decorate the muffins with it. You can also decorate the cupcakes with colorful sugar sprinkles, a dried banana chip or something similar.