Cook pasta according to packet instructions. Drain, and set aside.
In a large frying pan, heat oil over medium-high heat. Sauté the onions and garlic. Stir in the tomatoes, chicken, basil, salt and chillies. Reduce heat to medium, and cover frying pan. Simmer for about 5 minutes, stirring frequently.
Toss sauce with pasta to coat and heat through. Serve with Parmesan.