Wash the Kasseler, dab dry and season with pepper. Clean, wash and roughly cut the soup greens into pieces. Put meat and soup vegetables in a casserole. Bake in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for approx. 40 minutes.
Gradually add 1/2 litre of water. Peel onions, dice one finely. Heat 1 teaspoon of oil in a saucepan. Fry the diced onions in it until transparent. Add sauerkraut, bay leaf and juniper berries.
Add apple juice, bring to the boil and braise for about 30 minutes. Peel, wash and halve the potatoes. Cook in boiling salted water for about 20 minutes. 2. cut onion into fine rings. Heat 1 teaspoon of oil in a pan.
Fry the onion rings in it until golden brown and take them out. Warm up the milk. Drain, steam and mash the potatoes. Stir in milk, season with salt and nutmeg. Take out meat and keep warm.
Pass the frying stock and vegetables through a sieve. Bring the sauce to the boil, season with salt and pepper. Cut the smoked pork loin into thin slices. Arrange sauerkraut, mashed potatoes, meat and sauce on plates.
Garnish with parsley and onion rings.