About 4 pounds beef marrow and knuckle bones
3 pounds meaty rib or neck bones
4 or more quarts cold water
½ cup vinegar
3 onions, coarsely chopped
3 carrots, coarsely chopped
3 celery stalks, coarsely chopped
Several sprigs of fresh thyme, tied together
1 teaspoon peppercorns, crushed
1 bunch parsley
Place the bones in a very large pot with vinegar and cover with water. Let stand for 1 hour. Meanwhile, place the meaty bones in a roasting pan and brown at 350degrees in the oven. When well browned, add to the pot along with the vegetables. Pour the fat out of the roasting pan, add cold water to the pan, set over a high flame and bring to a boil, stirring with a wooden spoon to loosen up coagulated juices. Add this liquid to the pot. Add additional water, if necessary to cover the bones; but the liquid should come no higher than within one inch of the rim of the pot, as the volume expands slightly during cooking. Bring to a boil. A large amount of scum will come to the top, and it is important to remove this with a slotted spoon. After you have skimmed, reduce heat and add the thyme and crushed peppercorns.
Simmer stock for at least 12 and as long as 72 hours. Just before finishing, add the parsley and simmer another 10 minutes.
You now have a pot of rather repulsive-looking brown liquid containing globs of gelatinous and fatty material. It doesn’t even smell particularly good. But don’t despair. After straining you will have a delicious and nourishing clear broth.
Remove bones and strain stock into a large bowl. Let cool in the refrigerator and remove the congealed fat that rises to the top. Transfer to smaller containers and to the freezer for long-term storage.