Melt the butter and chocolate in a double boiler. In the meantime, puree the bananas, add the flour, sugar, vanilla sugar, salt and baking powder. Add the egg with the butter / chocolate mixture and stir everything into a homogeneous mass. Cut the Snickers into small pieces and mix in.
Put 2 paper cases in each muffin tin and pour the batter into the molds. Bake at 180 degrees top / bottom heat (160 degrees hot air) for about 30 minutes on the middle rack. Let cool in the mold for 10 minutes and then let the muffins cool with a paper mold on a wire rack.