Place puff pastry slices next to each other on the work surface and allow to defrost. Lay on top of each other and roll out into a rectangle (25 x 30 cm) on a floured work surface. Fold the long sides over approx. 4 cm towards the middle. Cut the edges several times crosswise, prick the middle several times with a fork. Place the dough strips on a baking tray lined with baking paper and bake in a preheated oven (electric range: 200 °C/ gas: level 3) for approx. 25 minutes.
Whisk the egg yolk and cream and brush the edges of the pastry with it 10 minutes before the end of the cooking time. Clean, wash and halve the plums. Remove stone. Bring the plums, 20 g sugar and vanillin sugar to the boil. Cook for about 5 minutes at medium heat, stirring continuously. Let the compote cool down. Let dough strips cool down on a cake rack. Mix mascarpone, quark, remaining sugar, cinnamon and lemon juice. Spread cream on the middle of the dough strip. Pour compote over it.
Let the compote cool down. Let dough strips cool down on a cake rack. Mix mascarpone, quark, remaining sugar, cinnamon and lemon juice. Spread cream on the middle of the dough strip. Pour compote over it. Sprinkle cake with pistachios. Results in 8 pieces