Mix the chilli powder with the celery salt, brown sugar, red wine vinegar, worcestershire sauce, tomato ketchup, chicken stock and tabasco sauce. Deeply score the chicken and arrange in a flameproof dish. Pour over the chilli mixture, heat the grill to high and cook the chicken for 5 minutes. Reduce the heat and cook for 10 minutes on each side. Baste the chicken thoroughly with the chilli sauce and grill for a further 10 minutes or until the meat is tender and the juices run clear. Transfer the chicken to a warmed serving dish and spoon over any sauce from the grill pan. Top each portion with a generous dollop of natural yoghurt. Garnish with coriander or parsley sprigs and serve with a salad. Calories: 240 per serving