Preheat the oven to 160-180 °C for the chocolate muffins. Melt the butter.
For the chocolate muffins, sift baking powder into the flour and mix with cocoa and nuts in a bowl.
Mix the melted butter with vanilla sugar, sugar, and milk. Beat the eggs and stir them into the mixture. Add to the dry ingredients and mix lightly together with the chocolate chips.
The dough should be lumpy, not stirred until fluffy. Now work the batter quickly, do not let it stand too long or the muffins will not be fluffy.
Fill muffin tins two-thirds full with the chocolate mixture. Bake the chocolate muffins in the preheated oven for about 20 minutes.
Allow the finished chocolate muffins to cool for a few minutes before enjoying.