Remove the meat from the shinbone. Place the shinbone and marrowbones in boiling water, cook for five minutes, and drain well.
Place the bones and all the meat including trimmings in a large kettle. Add five quarts cold water and bring to a boil. Reduce the heat. Skim to remove foam and fat and continue to skim occasionally until foam ceases to rise.
Add the salt, peppercorns and onion. Trim the leek and split down the center without cutting through the root end. Wash well to remove any sand. Place the bay leaf in the center of the leek and sprinkle with the thyme. Tie the little bundle together with soft string and add to the kettle. Add remaining ingredients, cover loosely, and simmer gently for four to five hours.
Lift the bones and meat from the liquid. (The meat may be used for hash.) Strain the liquid through a double thickness of cheesecloth. If a richer, more concentrated flavor is desired, the stock may be reduced by simmering, uncovered, until it reaches the desired flavor.
Cool the stock quickly and chill it. The fat in the liquid will rise to the surface and form a hardened thin layer. Remove this before using the stock in recipes.