Heat gas grill to medium-high or prepare charcoal grill. In a small saucepan mix ketchup, hoisin, soy sauce, and sesame oil. Lightly coat grill with non-stick cooking spray or oil. Put chicken on grill bottom and baste with sauce. Close grill cover and cook 5 mins. Remove cover and baste generously and continue every 5 minutes for 20 mins. Serve with your favorite salads/sides.