First whisk the eggs, sugar, vanilla sugar, butter and buttermilk briefly. Mix in the flour, baking powder, baking soda and salt. Fold in the blueberries.
Put paper baking cases in a muffin tin. Preheat the oven to 175 degrees (top / bottom heat). Pour the batter into the molds. Bake for 20-25 minutes. Take out of the oven and sprinkle with sugar if you like.