Clean or peel and wash the soup greens. Cut carrots and leek into slices, celery into pieces. Peel and halve the onion.
Wash the meat, dab dry and remove any connective tissue. Season meat with salt and pepper all around. Preheat oven (electric cooker: 200°C/circulating air: 175°C/gas: level 3).
Heat the lard in a small roaster or casserole. Brown the knuckle of pork in it all around at high heat. Add vegetables and onion and fry briefly.
Dissolve the stock in 1/2-3/4 l hot water. Pour 1/4 l stock and wine to the knuckle of pork. Roast in the hot oven for about 2 1/2 hours. Add the rest of the stock little by little. Now and then cover the knuckle with the roast stock.
Remove the roast. Pour the roast stock through a fine sieve into a pot. Bring the stock to the boil. Stir the starch and 4 tablespoons of cold water until smooth and add to the boiling stock, simmer for 2-3 minutes.
Season the sauce with salt and pepper. Cut the knuckle parallel in slices from the bone. Add the sauce. Cole Slaw and pretzel taste good with it.