At Least 4 Days Before Cooking, combine meat, vinegar, horseradish and salt in a crock. Cover and place in the refrigerator, turning once a day, for at least 4 days and up to 10. The day of serving, preheat the oven to 325F. Place the meat, marinade, and onions in a heavy lidded pot. Add the chicken stock, cover and place in the oven to cook for 1 1/2 to 2 hours. When the meat is tender, remove the pot from the heat and remove the meat. Skim off as much fat as you can from the surface of the remaining liquid, pour the liquid over the meat and serve.

Michael Roberts - Prodigy Guest Chefs Cookbook