Bring water with broth, bay leaf, juniper berries and allspice to a boil and cook the knuckle of pork in it until the meat can be easily removed from the bone. Then remove the knuckle of pork, let it cool, remove the meat and cut it into small pieces.
Strain the broth and heat about 3/4 of it again in a pot but do not let it boil. Add the meat pieces and the vinegar and dissolve the gelatin in it. Pour the aspic into another container and refrigerate. Note: The amount of vinegar in the aspic depends on the taste. You should taste the aspic again before adding the gelatine and season it if necessary.
Serve with brown bread as a snack or with fried potatoes and salad as a main course.