Butter a 28 or 30 tart pan and line it with the puff pastry. Cleanly cut off the protruding edge with a knife.
Mix the quark, sour cream, eggs, sugar, vanilla sugar, vanilla paste and cornstarch. Fill into the mold. Decorate with fresh berries, e.g. blueberries or raspberries. Canned mandarins are also conceivable.
Bake in the preheated oven for approx. 40 minutes on the middle rack.
Let it cool down, but it also tastes slightly lukewarm.