Ingredients :

• The bones — This is the main ingredient, and the choice matters. Ask your butcher for beef shank or knuckle bones — these provide the most collagen. For chicken, save carcasses after a roast or buy them directly. The more joints and cartilage, the more the broth will gel. Marrow bones, chicken feet: they all work very well.
• Apple cider vinegar — Two tablespoons might seem strange in a broth. But vinegar helps extract minerals from the bones during the long cooking time — and no, you won’t taste it in the final result. Any store-brand apple cider vinegar will do; no need for a special brand.
• The vegetables — Carrot, onion, celery — the classic trinity. No need to peel anything, just cut into large chunks. It’s also a great way to use carrot tops, onion skins, or celery leaves that you usually throw away.
• The herbs — Bay leaf and peppercorns are the base. If you have thyme or garlic lying around, add them. As for salt, wait until the end — the broth reduces slightly during cooking and can become too salty if seasoned too early.