Boil the potatoes in salted water as jacket potatoes, drain, peel and cut into slices.
Heat the clarified butter in a large pan, fry the diced ham and diced onion in it, dust with flour and deglaze with stock and milk. Stir vigorously so that the flour doesn`t clump. Stir in the processed cheese, season with nutmeg, pepper and salt, stir in the sour cream and let the potato slices soak for 5-10 minutes. Arrange on plates and sprinkle with chopped parsley.