Put the oil, onion, celery, garlic and a good pinch of salt and pepper in a saucepan over medium heat and cook for about 7 minutes until golden. Add the pancetta and chicken and stir constantly with a wooden spoon to break up any lumps. When the mince is cooked through, add the passata and simmer for 10 minutes. Season with sugar and any extra salt, pepper or sugar.
Meanwhile, cook the pasta to packet directions. Drain and toss with the sauce.
To serve, fold in parsley and top with grated parmesan.