Mix flour + cocoa + baking soda (baking powder) + salt + coffee in a larger bowl.
Melt the butter, whisk with sugar + vanilla sugar + eggs + milk. Add to the flour mixture together with the chopped chocolate, stir everything in well.
Prepare 12 muffin molds (grease or paper molds), pour in the batter, place a Ferrero Rocher in the middle of each, bake at 180 ° C for about 18 minutes.
Or as a surprise muffins: fill in the batter halfway, put a Ferrero Rocher in each, cover with batter.