In a medium saucepan, heat oil over medium heat and add horseradish, onions, pepper and garlic. Saute until translucent, 5 to 8 minutes. Add all other ingredients. Bring to a boil. Turn heat down, and simmer 1 hour. Strain through a double thickness of cheesecloth and store in a wooden cask, if possible. This is best if allowed to mature about a month before using.