Wash the meat and dab dry. Score the rind with a sharp knife in a diamond-shaped pattern and rub with salt and pepper. Place the knuckle of pork on a rack over the fat pan of the oven.
Sear in the preheated oven (electric: 225 ° C/ gas: level 4) for 30 minutes. Peel onions and cut into fine slices. After 30 minutes, put 200 grams of onion slices into the fat pan and pour on 1/4 litre of water.
Continue cooking at 200 grams (gas: level 3) for one hour. In the meantime, heat the fat in a pot and fry the remaining onion slices until transparent. Add the sauerkraut and steam briefly. Add 1/8 litre water and the apple juice.
Add laurel, juniper berries and cloves. Season with salt, pepper and sugar, bring to the boil, cover and cook over a low heat for 25 to 30 minutes. Wrap knuckle of pork in aluminium foil and keep warm.
Degrease frying stock. Pour on 1/8 litre water and beer. Pour frying stock through a sieve into a pot and bring to the boil. Stir in sauce thickener, bring to the boil again. Season to taste with salt and pepper. Season to taste with sauerkraut.
Arrange the knuckle of pork with the sauce and the sauerkraut. Bread dumplings taste good with it.