Cook the pasta in 3-4 l boiling salted water (approx. 1 teaspoon salt per litre) according to the instructions on the packet. In the meantime peel and finely dice the onion. Wash the meat, dab dry and cut into strips.
Heat the oil in a frying pan. Brown the chicken in it all around. Fry the onion briefly. Season well with salt, pepper and chilli powder. Add tomato paste and sauté briefly. Deglaze with chunky tomatoes.
Bring everything to the boil and simmer at medium heat for about 5 minutes. Stir in cream cheese.
Preheat oven (electric cooker: 200 °C/circulating air: 175 °C/gas: see manufacturer). Wash rosemary, dab dry, pluck needles and chop coarsely. Finely dice bread. Cut Mozzarella into thin slices.
Drain the pasta well and put it back into the pot. Mix with the chicken and tomato sauce and put into an ovenproof dish. Spread the mozzarella on the casserole. Sprinkle with rosemary and bread cubes.
Put butter in flakes on top. Bake in a hot oven for 15-18 minutes.