1. Preheat the oven to 190C/Gas 5.
2. Arrange the chicken breasts in a shallow roasting tin or baking dish. Tuck the shallots, garlic and olives in around the chicken and place the thyme sprigs on top.
3. Drizzle over the oil and season with salt and pepper.
4. Bake for 20 minutes, then remove from the oven and drizzle over the sherry vinegar.
5. Cook for a further 10 minutes, until the chicken is cooked through. Serve with a green salad.