Prepare chicken: Remove giblets from cavity. Rinse chicken under cold water and pat dry. Can leave whole or quarter.
Start with cold water: Place chicken in large stockpot. Add cold water to cover by 2 inches. Add apple cider vinegar.
Bring to simmer: Heat over medium-high until gentle simmer begins. Watch carefully—don't let it boil hard.
Skim foam: As foam rises to surface, skim off with large spoon or ladle. Continue skimming every few minutes for first 15-20 minutes.
Add vegetables: Once foam is mostly skimmed, add onions, carrots, celery, garlic, bay leaves, parsley, thyme, and peppercorns.
Simmer low and slow: Reduce heat to low. Maintain very gentle simmer with occasional small bubbles. Partially cover pot with lid ajar.
Cook: Simmer 3-4 hours, checking occasionally. Skim any additional foam or fat. Keep simmer gentle—don't let it boil.
Check doneness: After 3-4 hours, chicken should be falling off bones and broth deeply golden and aromatic.
Remove chicken: Carefully remove chicken with tongs. Place in bowl to cool. Once cool, remove meat from bones and save for other uses.
Strain broth: Place fine-mesh strainer (lined with cheesecloth for crystal-clear broth) over large bowl. Ladle broth through strainer.
Season: Add salt to strained broth and stir. Taste and adjust seasoning lightly—can add more when using in recipes.
Cool: Let cool at room temperature 30 minutes, then refrigerate uncovered until completely cold.
Remove fat: Once chilled, lift solidified fat layer off top with spoon. Save fat for cooking or discard.
Store: Transfer defatted broth to airtight containers. Label with date. Broth will gel when cold—this is normal and desirable.