Place 2 paper baking cups inside each other in the recesses of a muffin tray (12 recesses). Preheat oven (electric oven: 175 °C/circulating air: 150 °C/gas: see manufacturer). Wash and sort blueberries and drain well.
Whisk the eggs briefly in a large bowl. Add sugar, vanilla sugar, butter and buttermilk. Mix briefly with the whisk of the mixer. Mix flour, baking powder, baking soda and 1 pinch of salt and stir in briefly.
Fold in blueberries.
Spread the dough into the paper baking cups and bake in a hot oven for 20-25 minutes. Let the muffins cool down briefly, then lift them out of the cups and let them cool down.