Wash the potatoes and cook in boiling water for about 20 minutes. Cut the sausage into slices. Wash marjoram, shake dry, pluck leaves from stalks and chop coarsely. Wash and quarter apples, remove core. Cut quarters into slices. Peel and halve onions and cut them into thin slices.
Heat the oil in a frying pan. Fry the sausage for about 6 minutes while turning. Take out and drain. Drain potatoes, rinse and peel. Fry in frying fat in a pan for about 4 minutes, turning.
Add apples and onions and fry for another 6 minutes at medium heat. Add the sausage again. Season with marjoram, salt and pepper. Serve in the pan