Preheat your oven to 400°F (200°C).

Spread the chicken bones on a baking sheet and roast for 30-40 minutes, or until nicely browned. This step is crucial for developing a deep, rich flavor and color in your broth.

Transfer the roasted bones to a large stock pot. Add the quartered onion, chopped carrots, celery, smashed garlic, apple cider vinegar, peppercorns, bay leaves, and parsley.

Pour in enough cold water to cover all the ingredients by at least an inch or two. Adding the apple cider vinegar helps to extract minerals from the bones.

Bring the pot to a boil over high heat, then immediately reduce the heat to low. Skim off any foam or impurities that rise to the surface during the first hour of simmering.

Cover the pot partially (leaving a small gap for steam to escape) and let it simmer gently for at least 12-24 hours. The longer it simmers, the more nutrient-rich and flavorful it will become. Ensure it never reaches a rolling boil, just a gentle simmer.

Once the simmering time is complete, carefully remove the bones and vegetables using tongs or a slotted spoon. Discard the solids.

Strain the broth through a fine-mesh sieve into a clean pot or large heatproof bowls. For an even clearer broth, you can line the sieve with cheesecloth.

Allow the broth to cool slightly, then skim off any excess fat from the surface. You can reserve this fat for cooking if desired.

Let the broth cool completely before storing.