Peel and finely dice the onions. Clean, wash and cut the leek into rings. Drain the beans on a sieve. Cut the sausages into slices. Heat oil in a pot. Brown the onions and leek in it.
Roughly chop the sauerkraut and sauté. Season with caraway and paprika. Pour on broth, bring to the boil, cover and cook for about 10 minutes. Add beans and sausages and cook for another 5 minutes. Season sauerkraut soup with salt and pepper and serve