Preheat your oven to 200°C. Spray a large frying pan with a few sprays of low calorie cooking spray and heat. Season the chicken breasts with plenty of salt and pepper and fry for 6 minutes on each side then set aside
Using the same frying pan (don't wipe) fry the onion and garlic until the onion starts to soften. Add the Balsamic, tomatoes and courgette (they'll bubble and that's ok) cook for 5 minutes stirring frequently
Add the basil and return the chicken to the pan, cook for 3 minutes on each side
After 15 minutes place the cheese on top of the chicken and cook for a further 5-10 minutes. Use a thermometer to check your chicken breast is cooked through before serving (needs to get to 74°C for a couple of minutes)