Boil beef in salted water for about an hour.
For the sauce, spasser the flour in butter, add 300 ml of meat broth and bring to a boil. Then add sour cream, grated horseradish and salt to taste. Mix well and cook for another minute.
Cut the meat into slices, put in a roasting pan, pour the sauce and put in the oven for 20 minutes at 180 degrees.