01 - For a deeper, richer flavor, roast the beef bones at 400°F for 30 minutes before simmering. This step is optional but highly recommended for developing color and complexity.
02 - Place the beef bones in a large stockpot or slow cooker. Add the roughly chopped carrots, celery, quartered onion, smashed garlic, bay leaves, fresh parsley, and whole peppercorns.
03 - Pour in the apple cider vinegar and 12 cups of cold water, ensuring all bones and vegetables are fully submerged.
04 - Bring the mixture to a gentle simmer over medium heat. During the first hour, use a skimmer or ladle to remove any foam or impurities that rise to the surface.
05 - Reduce the heat to low and simmer uncovered or partially covered for at least 12 hours. Check periodically and add water as needed to keep the bones submerged. The longer the simmer, the richer and more gelatinous the final broth will be.
06 - Carefully strain the broth through a fine-mesh sieve or cheesecloth into a large container. Discard all solids and season the strained broth with salt to taste.
07 - Allow the broth to cool to room temperature, then refrigerate. Once chilled, the fat will solidify on the surface and can be easily skimmed off if desired. Store in the refrigerator for up to 5 days or freeze for up to 3 months.