Whisk the margarine, sugar, vanilla sugar and eggs together. Add the eggnog, baking powder and flour. Also process with the mixer. Add the chocolate flakes and just fold in slightly. Pour the whole thing into the prepared hollows of a muffin tin or paper cases.
Bake in a preheated oven at 180 ° C for about 20 minutes.
You can top the muffins with chocolate icing or powdered sugar, if you like.