Peel and wash the potatoes, cover and cook in salted water for about 20 minutes.
In the meantime peel and halve the onions and cut them into strips. Cut the sausage into thicker slices and remove the skin. Wash marjoram, shake dry, pluck leaves from the stalks and chop.
Wash the apples, grate them dry and cut out the cores with an apple corer. Cut apples into rings.
Heat 1 tablespoon of oil in two large pans. Fry the apple slices for 3-4 minutes while turning. Take out, keep warm. Fry the sausage slices in hot frying fat for 3-4 minutes, turning them over, take them out and keep them warm.
Fry onions in frying fat for about 2 minutes.
Meanwhile drain the potatoes. Add milk and butter and mash to puree. Stir in marjoram. Season to taste with salt and nutmeg. Spread the mashed potatoes on plates. Arrange apples, sausage and onions in towers.