Heat onions, garlic and whiskey in a pan, but do not boil. After about 10 minutes, take it off the stove, light it and wait until the flame has gone out. If that doesn`t work, adding a dash of whiskey won`t do any harm. Then add all the other ingredients, bring to the boil briefly and leave to stand over medium heat for about 20 minutes. Stir again and again. If you prefer a smoother sauce, you can put it through a sieve at the end. Otherwise just pour it into boiled glasses or bottles and store in the refrigerator. Lasts for several weeks. After the barbecue season, it is mostly used up.
The ingredients may be a bit unusual, but they are worth getting. I`ve always brought Liquid Smoke with me from the States. It is now also available in Germany through various online shops. Lasts forever and you only need very small amounts.