Peel, quarter, core and dice the apples. Heat butter in a pot. Steam diced apples for about 2 minutes while turning. Add sugar and continue steaming for about 3 minutes. Season with cinnamon and lemon juice.
Let it cool down. Mix apple-butter mixture with quark, breadcrumbs and 1 egg yolk. Roll out the puff pastry on the foil. Quarter the dough lengthwise and crosswise to form 9 rectangles. Roll out the rectangles slightly larger lengthwise on a floured work surface. Brush the edges of the dough with water. Spread the quark mixture on one half of the dough sheets, fold the other half over and press down well. Make several cuts of about 1 cm on one long side. Put curd combs on a baking tray lined with baking paper. Whisk 1 egg yolk with 1 tbsp.
Spread the quark mixture on one half of the dough sheets, fold the other half over and press down well. Make several cuts of about 1 cm on one long side. Put curd combs on a baking tray lined with baking paper. Whisk 1 egg yolk with 1 tbsp. water, spread a thin layer on dough pockets. Bake in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 12-15 minutes until brown. Let cool on a cake rack and dust with icing sugar
Waiting time approx. 20 minutes