Bring 4 cups of the beef broth, the beef shank, and onion to boil in large pot. Reduce heat, cover, and simmer until meat is tender, about 1 hour 30 minutes. Remove meat, then let soup cool, then chill in fridge at least 4 hours. Spoon solidified fat from top of soup and discard.

Transfer meat to work surface; trim fat, and bone and discard. Chop meat, and store in wrapped bowl in fridge until needed.

Return soup pot to stove, add last 4 cups of broth, beets, carrots, and potato, and bring to boil. Reduce heat, cover, and simmer until vegetables are tender, about 30 minutes. Stir in meat, cabbage and 1/2 cup dill; cook until cabbage is tender, about 15 minutes. Season to taste with salt and pepper, then stir in vinegar.

To serve; ladle soup into bowls, and top with sour cream and remaining 1/4 cup dill.