Mix the quark with the eggs and 3 tablespoons of sugar until smooth. Mix the buttermilk with 2 tablespoons of sugar and the vanilla sugar. Peel and core the apples and cut into wedges. Cut the rolls into thin slices.
Grease a baking dish with butter. Layer the rolls, quark, apples and raisins in the pan, layer by layer. Finally pour the buttermilk over it and cover with flakes of butter. Put the pan in the cold oven, set the temperature to 200 degrees and bake the casserole for about 45 minutes.