Mix the nuts, flour, sugar, baking powder, salt and vanilla sugar together well. Add margarine. Mix briefly. Add orange juice and stir vigorously for a minute. Briefly mix in the chocolate.
Line a muffin tin with paper liners. They are important as the muffins are very fluffy. Put about one tablespoon of batter in a mold, put a teaspoon of jam on top and cover again with one tablespoon of batter. Do the same with the rest of the dough.
Bake muffins for about 20 minutes. They`re done when they get a light tan on top. Let cool in the tray. Take out carefully, dust with icing sugar if you like and serve.