Step 1Wash the chicken pieces and pat dry. If making schmaltz, remove skin from the whole chicken and set aside. Otherwise leave the skin on.
Step 2Place the chicken, leek, parsley sprigs, parsnips, dill, carrots, bay leaves, celery, peppercorns and onion in a deep pot and cover with cold water. Bring to a boil.
Step 3Reduce the heat and simmer, skimming the foam that forms on the top surface until it stops appearing. Simmer until the whole chicken is completely cooked, about 30 to 45 minutes. Remove the whole chicken and the wings carefully and cool.
Step 4Simmer the broth for 15 minutes longer and strain through a fine mesh strainer, discarding the solids. When the chicken is cool, remove the meat from the bones. Discard the bones. The chicken meat may be added back into the broth or saved for another use.
Step 5Chill overnight. Remove solidified fat from the top before heating.