Bring the milk to the boil, stir in the rice and cook on a low heat. Then let it cool down.
Mix the butter with sugar until foamy, add the eggs and the quark. Preheat the oven to 200 degrees. Add the rice pudding and pour half of the mixture into a baking dish. Then add the blueberries (not defrosted), do not stir.
Spread the rest of the quark rice mixture on top. Bake for 45-60 minutes, depending on the type of oven. Check every now and then, the casserole should get a nice, golden yellow color.
Can be eaten as a main course or cold as a dessert.