In a medium-size saucepan, heat the oil over medium heat. Add the onion and garlic and saute until tender, about 5 minutes. Add the ketchup, ¼ cup of the whiskey, vinegar, Worcestershire sauce, molasses, mustard, soy sauce, hot sauce or Tabasco, black pepper, and cayenne. Mix thoroughly. Cook for 2 hours in the smoker or add the liquid smoke and simmer for 20 minutes over low heat on the stovetop. Stir in the remaining ¼ cup whiskey. Use as a baste or a finishing and table sauce on pork, beef, and chicken. This sauce also is good in baked beans. It will keep for several weeks in the refrigerator.