Soak 2 slices of toast in cold water. Peel and finely chop the onions. Knead minced pork, 1/3 onions, egg, squeezed toast, a little salt and pepper. With moistened hands form approx. 8 meatballs.
Heat 2 tablespoons of oil in a frying pan. Fry the meatballs for 4 minutes on each side. Clean, wash and cut the savoy cabbage into strips. Peel, wash and roughly grate the carrots. Heat 1 tablespoon of oil in a saucepan.
Brown the rest of the onions in it. Add cabbage and carrots and fry for about 5 minutes. Add 1/4 litre of water and bring to the boil. Stir in 1 teaspoon of broth. Season vegetables with salt and pepper. Cover and stew for about 15 minutes.
Heat 3 tablespoons of butter in a saucepan. Sprinkle with flour and sauté briefly. Deglaze with milk and 1/4 litre water, bring to the boil. Stir in 1 teaspoon of broth and let it simmer for 3-5 minutes. Season sauce with salt, pepper and mustard.
Finely crumble 2 slices of toast. Season the cabbage again and fill it into a large greased casserole dish. Spread the meatballs on top. Pour béchamel sauce over them. Sprinkle toast crumbs over it. Add 2 tablespoons butter in flakes.
Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for about 30 minutes.