In a large baking dish combine the halved cherry tomatoes with 3 cloves of garlic, 2 tbsp olive oil and 1/4 tsp salt & pepper. Bake in the oven at 180C/350F for 20-25mins, or until they soften and release their juices (they should be a little wrinkly).
Scoop out 1/3 of the tomatoes and store to one side. Pour the rest into a blender, ensuring you scrape in all those lovely juices. Add chicken stock and basil, then blend until smooth.
Horizontally slice each chicken breast right through the centre to create 4 even-sized chicken breasts. Coat all over in oregano, garlic powder, salt and pepper.
Add 1 1/2 tbsp olive oil to a large pan over medium-high heat. Add the chicken and fry both sides for a few mins, or until golden on the outside and just about cooked through the centre. Remove and place chicken to one side.
Lower heat to medium and add 2 tbsp tomato puree. Fry for a minute or so, then pour in the tomato sauce. Add the mascarpone and give it all a good stir until everything is well blended.
Stir in any resting juices from the chicken then add the chicken back in. Baste it in the sauce then top with the leftover tomatoes and some extra basil!