Remove the skin from the onion and chop finely. Rinse the potatoes and kohlrabi. Cut both into sticks.
Heat oil, sauté vegetables in it. Extinguish with clear soup and cook for 15 minutes with closed lid.
Cut sausages into slices. Remove about half of the vegetables from the clear soup. Grind the remaining vegetables in the clear soup.
Season the soup with salt and freshly ground pepper. Add vegetables and heat sausage slices. Sprinkle with parsley.