4 lb Rump Roast; Beef, Boneless
2    Onions; Thinly Sliced
8    Peppercorns
4    Cloves; Whole
1    Bay Leaf
1 c  White Vinegar; Mild
1 c  Water
1/2 c  Cider Vinegar
1/4 c  Vegetable Oil
1/2 ts Salt
2 c  Water; boiling
10    Gingersnaps
1/2 c  Sour Cream
1 tb Unbleached Flour

Place the beef roast in a deep ceramic or glass bowl. Add onions,
peppercorns, cloves, and bay leaf. Pour white vinegar and cider vinegar
over the meat; chill, covered, for 4 days. Turn meat twice each day. Remove
the meat from the marinade, dry it well with paper towels, and strain the
marinade into a bowl. Reserve onions and 1 cup marinade. In a Dutch oven
brown the meat on all sides in hot vegetable oil. Sprinkle meat with salt.
Pour boiling water around the meat. sprinkle in crushed gingersnaps, and
simmer covered for 1 1/2 hours. Turn often. Add 1 cup of reserved marinade
and cook meat 2 hours or more, until tender. Remove the meat and keep it
warm. Strain the cooking juices into a large saucepan. In a small bowl mix
sour cream with flour. Stir it into the cooking juices and cook, stirring,
until sauce is thickened and smooth. Slice meat in 1/4 inch slices; add to
hot gravy. Arrange meat on a heated plater and pour extra sauce over it.