Finely chop the onions and sweat in the oil until translucent. Cut the kohlrabi and potatoes into cubes, add to the onions, deglaze with the stock and simmer for 20 minutes.
Mash the soup with a potato masher so that the soup becomes creamy. Dissolve the processed cheese in it. Stir in the finely chopped parsley and season with nutmeg, salt and pepper. Wiener sausages can be served with it.