Wash blueberries and dab dry. Cream butter, sugar, vanilla sugar and salt with the whisk of the hand mixer
Add the egg and mix. Mix flour and baking powder and stir in. Carefully knead in blueberries
Using a tablespoon, spread about 10 piles of dough on each of two baking trays lined with baking paper. Bring the piles of dough slightly into a round shape. Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for approx. 10 minutes each in succession
Let cookies cool down on the tray
Waiting time approx. 1 hour