Beat butter and sugar until frothy, add egg and vanilla and mix well.
Mix 2:
Sieve flour, baking powder and salt into a separate bowl.
Mix 3:
Mix the milk and yoghurt briefly with the hand mixer.
Flour blueberries in a small bowl.
Add mixes 2 and 3 to mix 1 alternately in small steps (2-3). Stir everything until everything is moistened. Finally fold in the blueberries until the fruits are evenly distributed in the batter.