Cut off the peel of the bread and soak it in milk. Chop the onion coarsely and fry until golden brown.
Add lightly pressed bread and onion to the minced meat, pass everything together through a meat grinder. Add salt, pepper, seasoning to taste, egg and mix well. Then beat off the minced meat and put it away in the cold.
Peel the onion and mushrooms for the filling.
Chop the onion very finely, the mushrooms into small cubes.
Fry the onion in vegetable oil until golden brown,
add the mushrooms, season with salt and pepper and fry until the liquid evaporates.
Put the filling in a bowl and cool. Grate a little cheese on a coarse grater, about 2 tbsp.l., and add to the filling. Add finely chopped greens.Mix it.
Grate the remaining cheese on a fine grater.
Shape the minced meat into balls and place them on a greased baking sheet,
Flatten with your hands, giving a round shape, and make depressions on top. Lightly fry the meatballs from the bottom.
Place the fried meatballs in a baking dish. Put the filling in the recess, smear with mayonnaise or sour cream, sprinkle with cheese and put in a hot oven.
Bake until cooked.
Serve one or two meatballs per serving with potatoes and fresh vegetables.