Wash the smoked pork shank and fresh spare ribs.

Place the meat in a large pot and cover with 8 cups of water.

Simmer the meat until tender, approximately 1 hour.

Add the chopped onion, diced potato, and sliced carrot to the pot.

Continue simmering until the vegetables are tender, about 15 minutes.

Remove the meat from the pot.

Press the cooked vegetables through a sieve.

Return the meat and pressed vegetables to the kettle.

Add the chopped mushrooms and sauerkraut to the soup.

If the sauerkraut is very sour, rinse it in cold water before adding it.

Simmer these ingredients until the sauerkraut is tender, about 20 minutes.

If using cooked, dried, or canned mushrooms, add the mushroom liquid to the soup.

In a separate pan, cook the finely chopped onion in the hot fat until tender.

Stir in the flour and brown it lightly.

Pour some soup liquid into the flour mixture, stir until smooth, and return it to the soup.

Add the sour cream to the soup.

Season with salt and pepper to taste.

Bring the soup to a boil.

Flavor with chopped dill or parsley.

Serve the meat as a separate course, or place a small slice of it into each bowl of soup.

Serve the soup with rye bread.