Wash the potatoes and cook in boiling water for about 20 minutes. In the meantime, wash and clean the leek and cut it into rings. Wash parsley, shake dry and chop finely, except for something to garnish.
Melt the fat in a pan. Add flour, sweat. Add stock and cream while stirring. Bring to the boil and simmer for 2-3 minutes. Season with salt, pepper and nutmeg. Add leek and simmer for another 5-6 minutes at low heat.
Drain the potatoes, rinse with cold water and peel. Leave to cool.
In the meantime, pat the meat dry and season with salt and pepper. Heat oil in a pan. Sauté the smoked pork steaks on each side for about 2 minutes. Place them side by side on a baking tray. Coarsely grate potatoes and cheese.
Mix with chopped parsley. Season to taste with salt and nutmeg. Spread the mixture over the Kasseler steaks. Gratinate in a hot oven on the grill step for about 5 minutes.
Season leek-cream vegetables with salt and nutmeg. Arrange with steaks on plates. Garnish with the rest of the parsley. Sprinkle with nutmeg if necessary.