Wash the potatoes thoroughly and cook in plenty of boiling water for 15-20 minutes. Meanwhile clean, wash and cut leek into rings. Bring the stock to the boil and cook the leek for 5-6 minutes.
Pour onto a sieve and collect the broth. Cut the cured pork into cubes. Heat 10 g fat in a saucepan and braise the diced Kasseler in it. Take them out and put the rest of the fat in the pot
Sweat flour in it, add broth and milk while stirring and bring to the boil. Add marjoram and let the sauce simmer for 4-5 minutes. Stir in mustard and season with salt and pepper. Add leek and smoked pork loin to the sauce.
Drain the potatoes, rinse under cold water and peel the skin. Put the potatoes in a greased casserole dish, pour the sauce over them and sprinkle with cheese. Bake in the preheated oven (electric oven: 200 °C/ gas: level 3) for 25-30 minutes.
Serve garnished with fresh marjoram as desired.