Place 1 sheet of strudel pastry on a clean dish towel and brush it with melted butter. Cover it with a 2nd sheet of strudel pastry, and also brush this with butter and sprinkle 1/2 tablespoon brown sugar. Place a 3rd sheet of strudel pastry on top of this, brush again with butter, and sprinkle this with another 1/2 tablespoon of brown sugar and cover with a 4th sheet of strudel pastry. Pour half of the quark mixture in the lower third onto the pastry. In doing so, leave a 3 cm wide pastry strip uncovered. Use the dish cloth to roll the pastry around the quark filling and place the roll on a baking tray lined with baking paper. Process the 4 other sheets of strudel pastry in the same way, and place them on the baking tray. Brush the strudel with the remaining butter.