Place paper cases in the hollows of the muffin tin and preheat the oven to 200 ° C top and bottom heat or 175 ° C fan oven.
Sift the flour, baking powder and baking soda and mix well.
Chop the chocolate into small pieces.
In a second bowl, beat the egg with sugar until frothy and stir in the vanilla sugar, oil, lemon yoghurt, lemon juice and pulp. Fold in the flour mixture and carefully fold in the chopped chocolate.
Pour the batter into the molds and bake for 25-30 minutes.
When the muffins are golden brown, take them out of the oven, let them cool and enjoy.