Pierce the sausages with a fork several times, bring to the boil with cold water, an onion and spices, simmer gently for 20 minutes. In the meantime, peel the potatoes and cut into small cubes.
Remove the onion from the broth, discard. If necessary, scoop the boiled fat from the broth. Add the potatoes to the soup and cook for about 25 minutes.
Peel the two remaining onions and cut into small cubes. Heat the clarified butter, roast the onion cubes brown and add to the potato soup at the end of the cooking time. If desired, mash the potatoes and serve.