Cut the chicken into small bitesize pieces, season with salt and pepper and set aside. Heat 1 tbsp of the oil in a wok, or wide frying pan, and fry the onion for 3-4 minutes. Stir in the garlic and fry for an additional 1 minute. As the onion is cooking bring a saucepan of water to the boil with salt and 1/2 tbsp of olive oil. This will help stop the tagliatelle from sticking together.