Remove all skins and fat from the meat. Clean, wash and chop the greens. Bring vinegar, 1/8 litre water, porcini mushrooms and spices to the boil and allow to cool. Put meat and soup vegetables in a bowl and pour wine and stock over them.
Cover and leave to marinate in the refrigerator for 2 days. Turn from time to time. Remove the meat and dab dry with kitchen paper. Season with salt and pepper. Heat oil in a roasting pan and fry the meat in it.
Add the marinade and braise at low heat for 1 1/4 hours. Clean and wash the Brussels sprouts and cook in salted water for 20 minutes. Wash, quarter, core and cut apple into pieces. Heat 10 g butter in a saucepan and sauté the apples briefly in it.
Clean, wash and slice the mushrooms. Sauté in the remaining butter. Remove the roast, pour the roast stock through a sieve to the mushrooms and bring to the boil. Stir in the sauce thickener, bring to the boil again and season with salt and pepper.
Drain the Brussels sprouts and mix with the apple slices. Season with nutmeg. Cut the meat open and arrange on a plate with the sauce and the Brussels sprouts. Garnish with parsley. The rest of the sauce is extra.
Spätzle are delicious with it.