If cooking in the oven preheat to 180*C/350*F/ gas mark 4.
Heat the butter and oil in a flameproof casserole dish brown the chicken all over and remove (this should take around 10 mins).fry the onions and garlic gently until soft in the remaining fat in the casserole, then add the tomato purée and cook gently for a few minutes before adding the olives. Return the chicken to the casserole and then add the salt & pepper. Pour over the alcohol or stock and vinegar. Cover and cook on top of the stove or in the oven for about 1 1/4 hrs. Sprinkle with herbs just before serving. Serve with rice