Sort the blueberries, wash and drain if necessary. Mix sugar, vanillin sugar, salt, flour and baking powder in a mixing bowl. Add egg, yoghurt, milk, oil, cinnamon and nutmeg. Knead to a smooth dough with the dough hooks. Fold in blueberries
Grease the muffin tin (for 12 pieces of approx. 7 cm Ø each) (alternatively place 2-3 paper baking cups inside each) and fill each with 3/4 of the dough. Bake in a hot oven (electric cooker: 200 °C / convection oven: 175 °C / gas: level 3) for approx. 30 minutes. Let the muffins cool down a little and then take them out of the tin
Heat the jam. Spread the muffins with jam and sprinkle with sugar crystals. Serve in paper sleeves as desired. Serve with vanilla ice cream