In one bowl, mix the flour, sugar, vanilla sugar, baking powder, and a pinch of salt.
In another bowl, whisk together the milk (or sparkling water), oil, and eggs.
Then, whisk together the ingredients from both bowls. Do not mix for long, just until the ingredients are combined.
Line the muffin tray with cupcake liners. Fill them with batter until about ⅔ of the height of the liner.
Place a few blueberries on each muffin (Do not press them into the batter).
Bake the muffins in a preheated oven for about 20-25 minutes, until a toothpick comes out dry, at a temperature of 200°C (top and bottom heat). After baking, remove the muffins from the oven and leave them in the pan for 5-10 minutes. Then, remove them from the pan and place them on a wire rack to cool completely.
You can dust the cooled muffins with powdered sugar.