Put all the ingredients for the marinade from onion to wine vinegar in a saucepan. Bring to a boil, cook for 6 minutes and let cool.
Cut the rind off the meat so that the marinade can penetrate better. Place the meat in a saucepan that just fits. Pour the cooled marinade over it. Let the meat marinate for at least 5 days, preferably 1 week. Turn every day.
Before preparing the roast, pat dry with kitchen paper. Save the marinade. Salt the roast and place in a frying pan. Insert a meat thermo. Put the roast in the oven preheated to 175 °. When the meat is browned, pour the marinade over it. The roasting time is between 2 and 2.5 hours. The meat is definitely done when the thermo shows 85 °.
Strain the sauce in a saucepan. Keep the roast warm. Knead a dumpling out of butter and flour and beat into the sauce with a whisk. Cook for a few minutes over a mild heat.