Clean, wash and chop the potatoes and carrots. Clean only the white part of the leek, wash, drain and cut into small pieces (approx. 250 g). Use the green part for other purposes. Wash the marjoram, shake dry and pluck off the leaves. Chop the leaves, except for a little to garnish.
Heat the fat in a large saucepan and sauté the potatoes, carrots and leek in it. Deglaze with broth, add marjoram and bring to the boil. Cover and simmer for 20-25 minutes.
Heat the oil in a pan and fry the Nürnberger in it until golden brown. Take out and let cool down. Wash chives and parsley and shake dry. Cut the chives into fine rolls. Remove the leaves from the parsley and chop them. Mix chopped herbs and crème fraîche, season with a little salt and pepper.
Cut the Nuremberg sausages into diagonally thin slices. Heat the pan with the frying fat, fry the sausage slices crisply while turning them. Place on kitchen roll and let drain. Puree soup, season with salt and pepper and divide into 4 deep bowls. Add a dash of herb crème fraîche and sausage chips to the soup. Garnish with marjoram.