Knead the minced meat with the chopped onion, black pepper, caraway seeds and salt to taste.
Form meatballs and press indentations into them. In the middle of each meatball, place 1 tablespoon of mushrooms (chopped and steamed in butter). Place 1 or 2 cubes of Kashkaval on top and cover the opening with minced meat.
Gently press the meatballs and roast them on a very hot grill.