Wipe beef with damp paper towel, cut into 1 1/2" cubes. Peel and slice onions (3 cups). Heat oil in large pot on high. Add beef cubes in single layer, saute on medium heat. Remove brown beef, set aside. Continue until all beef is browned.
Add onions to beef drippings, cook until golden. Return beef to pan, add paprika, salt & pepper. Stir in 3/4 cup beef broth. Bring to boil, reduce heat to simmer for 2 hours or until beef is tender.
Drain saurkraut, peel potato & grade (3/4 cup). Heat butter in skillet saute onion until brown. Add potato, saurkraut, caraway seed, brown sugar, 2 cups boiling water. Simmer uncovered for 20 minutes or until liquid has evaporated.
In small bowl combine flour and remaining broth. Stir until smooth. Gradually add to beef mixture. Stir occasionally. Simmer uncovered for 15 minutes.
Before serving, stir in 1/2 cup of hot gravy & sour cream into small bowl. Add slowly to beef mixture. Stir to blend, do not boil.
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