For the crumbles, knead butter, 200 g flour, 150 g sugar and vanillin sugar with the dough hooks of the hand mixer. Put it in a cold place. Wash and sort blueberries. For the base mix quark, milk, oil, 50 g sugar and salt. Mix 300 g flour and baking powder and stir about half into the quark mixture. Knead in the rest of the flour.
Roll out the dough on a floured work surface to a rectangle (approx. 32 x 39 cm) and place on a greased baking tray (32 x 39 cm). Spread the blueberries first, then the crumbles on the dough. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for approx. 25 minutes. Remove the cake, let it cool down and cut it into pieces. Whipped cream tastes good with it
1 hour waiting time