Combine the ham bone or hock, onion, carrots, celery, garlic, parsley, peppercorns and bay leaf in a 6- to 8-quart pot. Cover with 3 quarts of cold water and bring to a boil over medium-high heat. Skim off any foamy bubbles from the surface. Reduce the heat to medium low and cook for 3 hours. (You just want to see a few bubbles rise to the surface here and there.) Strain the stock through a fine-mesh strainer, then store in jars. The stock can be refrigerated for up to one week or stored in the freezer for up to three months.