Preheat the oven to 190/fan 170/gas 5
Lay each chicken breast out on a chopping board and using a very sharp knife, carefully slice a deep pocket in it, from front to back.
Using a teaspoon take a little oil from either the top of the pesto, or the jar of tomatoes and drizzle it onto the chicken breasts. You only need a tiny amount. Rub it into the meat well.
Drop a teaspoon of pesto into each chicken pocket and spread it around. (To avoid cross contamination, DO NOT put the teaspoon back into the jar of pesto if it has touched the raw chicken. Use a clean spoon).
Lay 4 sundried tomato halves inside each chicken pocket and move to a baking tray.
Serve with basmati rice and green beans and topped with the sprig of thyme.