Chop meat into one-inch cubes. Season with salt and pepper and let stand for an hour. Spear on to skewers, allowing six pieces of meat per person. Alternate lean and fatty meat with onions. Broil under a very hot flame, or over charcoal until outside is well browned and sizzling. If broiled in the oven, sprinkle a little olive oil over meat before broiling so that it will not dry out.