Peel and finely chop onion
Wipe and slice mushroom
Dice pepper
Peel and crush garlic
Spray frying pan and add onion, pepper and mushrooms. Cook for 3-5 mins, covering and allow to sweat
Add garlic
Stir in tomato puree, tomatoes and oregano
Season. Cover and simmer for about 15 mins. Stir occasionally. The aim is to reduce to a thick paste. Put to one side
Line chopping board with cling film, lay chicken on top and cover with cling film. Using a rolling pin flatten the chicken
Spray frying pan and seal chicken
Place in casserole
Spoon tomato topping over each chicken breast
Cover and cook for 30-40 mins, check temperature
Sprinkle over cheese and cook until cheese is melted
Serve with salad