Clean and skin chicken whole. Wash and dry. Cut slits lengthwise over the breast portion and breadth - wise over the legs of the chicken. Make a fine paste of ginger, garlic and green chillies. Beat the curd, add tandoori masala, ginger, garlic, green chilly paste, lime juice, salt and mix well. Apply this mixture all over the chicken and keep it for about six hours. Apply the oil on chicken and cook in the tandoor or oven. Serve hot garnished with onion rings and slices of lime.