Let the dough sheets rest at room temperature for about 10 minutes. Meanwhile melt butter and spread a thin layer of butter on a baking tray (32 x 39 cm). Cut half of the strudel dough sheets in the middle with scissors. Place 1 whole and ½ sheet slightly overlapping on the baking tray and brush thinly with butter. Place 4 whole and 4 half sheets on top of each other in the same way and brush each with butter. Spread the rest of the half leaves on top and spread with butter
Separate eggs. Beat the egg whites until stiff, gradually add 125 g of sugar and continue stirring until the beaten egg white is shiny. Mix egg yolks, quark, mascarpone, crème fraîche, 125 g sugar and flour until smooth. Fold in the beaten egg white
Pour half of the mixture into a 2nd bowl and mix with vanillin sugar, coffee liqueur and 1 tablespoon of espresso beans. Spread the light and dark quark mixture in patches on the strudel dough, draw a marble pattern into the quark mixture with a fork. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for approx. 25 minutes. Cut the cake cold or lukewarm and sprinkle with 1 tbsp. espresso beans