Bring a large saucepan of water to the boil, add the tagliatelle and cook for 8–10 minutes until just tender, then drain into a colander.
Meanwhile, heat the oil in a large frying pan, add the chicken, onion and pancetta and fry for 10 minutes, stirring until golden. Chop the chicken livers, discarding any white cores, then add to the pan with the garlic and fry for 3 minutes.
Stir in the red wine, stock and tomato paste, then a little seasoning. Cook over a high heat for 3–4 minutes until the sauce is reduced slightly. Tear half the basil leaves into pieces and add to the chicken, then cook for 1 minute.
Stir the tagliatelle into the chicken mixture and reheat if needed. Spoon into shallow bowls and sprinkle with the remaining basil leaves and grated Parmesan.