Preheat the oven to approx. 180 ° C with circulating air.
Mix the flour, sugar, vanilla sugar and baking powder together, then add the oil, water and flavoring and stir to a smooth batter. Then stir in the chocolate.
Pour the batter into muffin molds, about 3/4 full. I recommend silicone liners as the dough can stick to the paper liners. Bake for about 25 minutes.
In any case, it makes more than 12 muffins, for me it was about 20, but that also depends on the size of the molds.