Clean the leek, wash it and cut it into rings. Drain the sauerkraut. Cut pineapple into small pieces. Heat lard. Brown leek and sauerkraut in it.
Season with salt and pepper. Add pineapple and fry for about 10 minutes more. In the meantime, wash and dry the pork loin. Tap a little flatter. Coat with mustard. Pluck the parsley and spread on the slices of Kasseler. Fold them over and pin them down. Fry in hot oil, turning over, for about 7 minutes. Season with pepper. Deglaze with 200 ml water.
Fold them over and pin them down. Fry in hot oil, turning over, for about 7 minutes. Season with pepper. Deglaze with 200 ml water. Add the gravy to the sauerkraut. Serve garnished with parsley. Tastes good with mashed potatoes