Clean and clean the mushrooms and cut them into slices. Peel, wash and chop the carrots. Peel and finely chop onions. Soak rolls in cold water. Knead minced meat, egg, half of the onions, squeezed bread roll and mustard, season with salt and pepper. Form 8 meatballs
Heat the oil in a pan and fry the meatballs for 2-3 minutes on each side. Take them out and put them in an ovenproof dish. Fry the bacon, carrots, remaining onions and mushrooms in the hot frying fat. Add 250 ml water, milk and cream, add stock and simmer for about 5 minutes. Stir in the sauce thickener and let it simmer for about 1 minute. Season to taste with salt and pepper. Pour sauce over the meatballs. Spread cheese on top. Cook in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 20-25 minutes
Sprinkle the meatballs with chopped parsley. Spätzle or potatoes taste good with it.