1.Heat half the oil in a frying pan over a medium heat until hot and fry the chicken pieces for 5 minutes, or until lightly browned all over. Remove the chicken from the pan with a slotted spoon, transfer to an ovenproof dish and set aside.
2.Add the onion, peppers, mushrooms, olives and tomatoes to the frying pan. Turn the heat down to low, and fry, stirring occasionally for 5 minutes until soft. Remove the vegetables with a slotted spoon and spoon them over the chicken.
3. Preheat the oven to 180ºC/350ºF/Gas 4. Heat the stock in a saucepan until boiling. Pour it over the chicken, cover the dish with a lid and bake for 1-1½ hours, or until the chicken is cooked through.
4. Remove from the oven and serve hot with rice or quinoa.