BARBECUE RIBS: TO BARBECUE THE RIBS: Preheat oven to 190ºC or light a charcoal grill. Defrost the braising liquid. Defrost the ribs or not; it's not important. Combine the sugar and vinegar in a 1 litre pot and place over medium heat on top of the stove. Cook until the vinegar reduces and forms a syrup with the sugar, about 8 minutes. Watch carefully as the syrup will suddenly darken in color. Immediately add the rib braising liquid, then the catsup, mustard, Worcestershire, cloves, chili powder and cayenne pepper. Cook, reducing the liquid until it has a thick sauce-like consistency. Remove from the heat and set aside. TO COOK RIBS IN THE OVEN, place ribs in a roasting pan, cover, place in oven and turn temperature to 180ºC . Cook for 30 minutes, basting with more barbecue sauce every 10 minutes. TO COOK ON THE GRILL, wait until the coals become white hot and pile them on one side of the grill. Place the ribs on the grill so they are not directly over the coals and cover the grill so that smoke collects inside. If your grill does not have a cover, improvise one out of aluminum foil. Cook for 30 minutes, basting with more barbecue sauce every 10 minutes. When ribs are well heated, remove to a platter and serve. Offer any additional barbecue sauce on the side.