- 7 pounds beef bones, such as oxtail, short rib, knuckle, and shank
- 6 quarts water
- 2 tablespoons red wine vinegar
- 3 onions, coarsely chopped
- 3 carrots, coarsely chopped
- 3 stalks celery, coarsely chopped
- 1 head garlic, cloves separated and peeled
- 2 cups parsley leaves
- 12 sprigs fresh thyme
- 2 bay leaves
- 1 tablespoon whole black peppercorns
- 1/3 cup dried mushrooms, such as porcini
- Preheat oven to 400 degrees F (200 degrees C).
- Arrange bones on 2 rimmed baking sheets and roast, turning occasionally, until well browned, about 45 minutes. Transfer bones to a 12-quart stockpot. Pour off fat from baking sheets, reserving 1 tablespoon. Add water and vinegar to pot and bring to a boil. Reduce heat and gently simmer, skimming off foam occasionally, 1 1/2 hours.
- Meanwhile, arrange onions, carrots, celery, and garlic on baking sheet (from roasting bones) and drizzle with reserved fat. Roast vegetables, tossing occasionally, until softened, about 40 minutes.
- Add vegetables to pot with bones, then stir in parsley, thyme, bay leaves, peppercorns, and mushrooms. Keep heat low enough that liquid barely simmers, and cook 12 hours (overnight).
- Strain soup through a fine-mesh sieve and discard solids. Skim any remaining foam and taste broth. To intensify flavor, transfer soup to a clean pot and boil to desired concentration.