Cut the ham into strips. Wash and chop the rosemary. Peel and chop onions and garlic.
Cut the chicken fillets and skin from the bone, wash and pat dry. Season with salt and pepper. Turn in flour, tap off excess flour. Heat oil in a large frying pan. Fry the fillets for 2-3 minutes on each side and remove.
Fry ham in hot frying fat until crispy. Fry rosemary, onions and garlic for about 3 minutes. Deglaze with wine and vinegar. Bring to the boil and reduce by half. Add canned tomatoes and juice.
Simmer everything open for about 20 minutes, chopping the tomatoes coarsely. Wash and quarter the tomatoes, add them about 5 minutes before the end of the cooking time and cook with them.
Season the sauce to taste with salt, pepper and sugar and pour into an ovenproof dish. Place the fillets in it. Bake in a hot oven (electric cooker: 200 °C/circulating air: 175 °C/gas: see manufacturer) for 25-30 minutes. Mashed potatoes taste good with it.