Adapted from Joy of Cooking
Preheat oven to 425ºF. Lightly oil a roasting pan.
Combine:
3 pounds meaty beef shanks, cut into 2-inch pieces or oxtails, split into chunks, or a combination
1 pound chicken parts, rinsed (backs, necks, wings, legs or thighs)
2 medium onions, quartered
2 carrots, peeled and thickly sliced
2 celery stalks, cut into 2-inch pieces.
Place everything in the roasting pan and roast, stirring occasionally to prevent burning, until the bones are well-browned, about 40-45 minutes. Transfer the meat and vegetables to a stockpot.
Place the roasting pan on the burner over medium heat and add about 2 cups of cold water to the roasting pan. Scrape up any browned bits on the roasting pan and then pour the water out of the roasting pan and into the stock pot. Add cold water to the stock pot to cover the meat and vegetables- around 14 cups of water.
Bring to a boil over medium heat, skim off any scum that forms as it cooks. Reduce the heat and simmer gently- uncovered. After about 30 minutes, add:
1 leek that has been split and thoroughly cleaned, and cut into 2-inch pieces
1 bouquet garni, including 1 clove
Simmer, uncovered, for 4 hours, skimming of any scum as it cooks. Also, add water if needed to continuously cover the meat and vegetables in the pot. Cook for 4 hours. Strain into a clean pot. Let cool, uncovered, then refrigerate. Remove the fat before using the stock.
Makes about 10 cups stock.