Cut pancetta into strips. Wash rosemary, dab dry, pluck needles and chop finely. Peel onions and garlic. Dice onions, crush garlic.
Cut the chicken fillets and skin from the bone, wash and pat dry. Season with salt and pepper. Turn in flour, shake off excess flour slightly. Heat the oil in a large frying pan. Fry the fillets for 2-3 minutes on each side and remove.
Fry the pancetta in hot frying fat. Stir-fry the rosemary, fennel seeds, onions and garlic for approx. 3 minutes. Deglaze with wine and vinegar, reduce by half over high heat. Add canned tomatoes together with the juice.
Simmer everything open at medium heat for about 20 minutes, while roughly chopping the tomatoes. Wash the cherry tomatoes, cut them in half and add them about 5 minutes before the end of the cooking time.
In the meantime clean and wash the cauliflower and divide it into small florets. Peel, wash and chop the potatoes. Preheat the oven (electric cooker: 200 °C/circulating air: 175 °C/gas: see manufacturer). Season tomato sauce with salt, pepper and 1 pinch of sugar and pour into an ovenproof dish.
Place the fillets inside and bake in a hot oven for 25-30 minutes.
Cover the potatoes and cauliflower and cook in salted water for about 20 minutes. Then drain. Add milk and butter and mash everything coarsely. Season to taste with salt and nutmeg. Serve the chicken fillets with cauliflower and potato puree.