Peel the onion, chop it finely and sauté in the clarified butter until translucent. Add the sauerkraut with the juice and season with caraway seeds, salt and pepper. Stir in a tablespoon of mustard and mix everything well. Deglaze with the vegetable stock. Reduce the temperature and let the cabbage simmer for 40 minutes. At the end the broth should have evaporated.
Fry the sausages in a tablespoon of oil and serve with the hot sauerkraut and a tablespoon of mustard.