Remove excess fat from chicken pieces as necessary. Place the chicken parts/bones in a large stock pot with the onion, carrot, celery, thyme, parsley, bay leaf and peppercorns. Wrap thyme, parsley, bay leaf and peppercorns in cheesecloth secured with kitchen twine for a bouquet garni if desired. Add enough water to cover the ingredients by 2".

Bring the mixture to a boil and immediately reduce the heat to medium low. Simmer uncovered for about 4 hours, skimming any scum off the top occasionally.

Remove the pot from heat and carefully strain into a large bowl using a fine mesh strainer and cool completely. If a layer of fat has formed at the top, remove it before storing.

Store chicken stock in the refrigerator or portion and freeze in air tight containers.