For the yeast dough, dissolve the yeast in the milk, cover and let it rest for about ten minutes. Mix flour, sugar and salt in a bowl. Add the yeast milk and oil and knead everything into a smooth dough with the dough hooks of the hand mixer. Cover the dough and leave to rise in a warm place for about 30 minutes. For the crumbles, mix flour, sugar and salt in a bowl.
Add the fat in small pieces and work everything into crumbles. Put them in a cold place. For the quark mixture, mix mascarpone, quark, whipped cream, sugar, lemon juice and zest, eggs and semolina. Knead the yeast dough well again. Roll out on a floured work surface to a rectangle the size of the fat pan (approx. 35x39 cm). Spread the fat pan with fat. Put yeast dough on top. Prick the dough several times with a fork and let it rise again for about ten minutes. Spread the quark mixture on the dough. Sprinkle with crumbles.
Put yeast dough on top. Prick the dough several times with a fork and let it rise again for about ten minutes. Spread the quark mixture on the dough. Sprinkle with crumbles. Bake in the preheated oven (electric: 200 °C/ gas: level 3) for 30-35 minutes. Let them cool down. Dust with icing sugar as desired