Melt the butter and let it cool. Then knead with quark, flour, baking powder and sugar to form a smooth dough. Press into a mold, form an edge and spread the blueberries on top.
For the topping, mix the cream, egg, powdered sugar, vanilla sugar and cornstarch and pour over the berries. Bake in a preheated oven at 180 ° C for approx. 35 minutes.