1. In a very large stockpot, heat oil over medium-high heat. Place as many chicken pieces as will fit into a single layer, skin side down (do not crowd - you'll need to brown in 3 or 4 batches) and cook, undisturbed, until the skin is golden, about 4 minutes. Turn the chicken pieces and cook, again undisturbed, until second side is golden, about 4 minutes longer. Transfer pieces to a large plate and repeat with remaining chicken, adjusting heat if pot threatens to scorch. Once all the chicken is done, remove all but 2 teaspoons fat from pot.
2. Return pot to medium heat, add onions and salt and cook, stirring frequently, until softened, about 4 minutes. Return chicken to pot, cover, adjust heat to medium-low, and simmer until chicken has released its juices, about 15 minutes.
3. Add carrots, celery, thyme, parsley, bay leaves, peppercorns, and water. Adjust heat to high and bring to a strong simmer. Skim surface foam, adjust heat to low, and simmer gently (make sure it's not boiling) until fragrant and flavorful, about 3 hours, skimming periodically as necessary.
4. Strain broth into a very large bowl or pot, pressing solids to release as much liquid as possible; discard solids. Refrigerate broth, covered, overnight or until fat has risen to surface and solidified. Remove and discard solid fat or reserve for another use. Use broth at once or refrigerate, covered, for 3 days, or freeze in portions as desired.
Source: Hannaford fresh Magazine, January - February 2012