Wash the oregano, dab dry, put something to garnish aside. Pluck the rest of the leaves. Cut bread into large cubes. Put oregano in a large casserole dish and sprinkle with 2 tablespoons of oil.
Roast in the preheated oven (electric cooker: 200 °C/ circulating air: 175 °C/ gas: level 3) for 12-15 minutes. In the meantime peel and chop the onion. Clean, wash and finely chop the pepperoni. Clean, wash and halve the mushrooms.
Wash the meat, dab dry and cut into cubes. Heat 2 tablespoons of oil and fry the meat all around. Season with salt and pepper. Add onion, pepperoni, mushrooms and herbs and fry briefly.
Add the tomato paste, sweat briefly. Coarsely chop the canned tomatoes and add them with the juice to the meat, simmer for 5 minutes. Add cream and season to taste with salt, pepper and sugar. Drain mozzarella and cut into pieces.
Wash, clean and slice the tomatoes. Spread chicken ragout on the bread. Cover with tomato and mozzarella slices. Bake in a hot oven at the same temperature for about 15 minutes.
Garnish with oregano set aside.