Soak toast in cold water. Peel onions and garlic and dice very finely. Clean the mushrooms and, depending on their size, possibly halve them. Squeeze the toast. Put minced meat, bread, eggs, half of the onions, 1 tbsp. tomato paste, some salt, pepper and pizza spice in a large mixing bowl.
Knead with the dough hook of the hand mixer. Shape approx. 18 meatballs with moistened hands. Heat 2 tablespoons of oil in a large frying pan and fry the meatballs in 2 portions for approx. 5 minutes, turning them over.
Pour into a wide ovenproof dish. Add 2 tablespoons of oil to the hot pan. First fry the mushrooms for 5-6 minutes, then add the garlic and the remaining onions and fry. Season with salt, pepper and oregano.
Pour on broth and cream. Add 1 tablespoon of tomato paste and tinned tomatoes. Coarsely chop the tomatoes with a spatula. Bring the sauce to the boil and simmer for about 5 minutes. Pour mushroom and tomato cream over the meatballs.
Sprinkle with cheese. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for approx. 30 minutes. Garnish with fresh oregano if desired. Ciabatta bread tastes good with it.