Peel and chop the potatoes. The roots - consisting of carrots, celery, parsley, kohlrabi - wash, peel and cut into small pieces.
Put the potatoes with the roots, except for the parsley, in a saucepan with water and bring to the boil. Add a little salt and pepper and add the marjoram (so that it forms a kind of carpet on the surface). Let everything cook well for about 1/2 hour.
Then mash all the ingredients. Possibly add a little milk to make it a little thicker and beat an egg in, it will bind a little more. Cut the sausages into small pieces and add. Season to taste and serve. Only distribute the parsley on the plates at the table.
Tips: You can also leave out a little bacon and add it, then you don`t need to add so much salt and it will be nice and spicy. The soup tastes best when it has been left to steep for a while.