Insert a whole clove in 2 onion quarters. Place onions and next 4 ingredients in large roasting pan. Bake, uncovered, in a preheated 450 F oven until bones are deeply browned (about 45 minutes), turning bones and vegetables occasionally. Transfer ingredients from roasting pan to 8-quart stockpot. Discard fat in roasting pan. Stir 2 cups water into roasting pan, heat and scrape to loosen any browned meat drippings. Pour hot liquid and 10 cups additional water over bones and vegetables. Bring to boiling. Simmer, partially covered, 30 minutes. Skim off any foam that rises to surface. Stir in next 8 ingredients. Simmer, partially covered, an additional 3 hours. Remove bones. (Remove meat from bones, refrigerated or freeze for future use). Strain broth through cheese cloth lined strainer. Stir in salt (optional). Refrigerate broth, leaving fat layer on surface until ready to use. Cover broth when cool.