Soak six wooden skewers in cold water for 15 minutes. This prevents them from burning when they are heated.
Soak the chicken pieces in the beer.
Cover with cling film and refrigerate for 2-3 hours.
Mix the oil, chilli powder, paprika, salt, garlic and black pepper together in a large bowl.
Fold in the chicken pieces, coating them well.
Skewer the chicken and place directly on the oven shelves or under the grill for 10-15 minutes, turning and brushing or basting them with oil at least once during grilling. Or place on a barbecue. Make sure the chicken is cooked right through, then remove from the grill.
Serve hot with mayonnaise or a tomato relish.
Serve hot topped with the onion slices and sliced green chillies.