Rinse the chicken pieces well, and remove any excess fat. Put them in a large stockpot with 8 quarts cold water. Bring to a boil, reduce heat so the liquid is simmering, and cook 1 hour, skimming and discarding any scum that rises to the surface.

Meanwhile, using tongs, brown the onion halves over a burner flame (or in a cast-iron pan) until well browned all over.

After simmering the chicken an hour, add the onion, garlic, carrot, celery, parsley, bay leaves, peppercorns, and salt to the pot. Partially cover, and simmer until broth is flavorful and liquid level is reduced by about half, about 2 hours more.

Strain the stock, let it cool to room temperature, then chill until cold. When it’s cold, remove the layer of solidified fat on top and discard.