I think the healthiest chicken stock is made from chicken bones! I save all my bones in the freezer, until I have almost a potful. Then they're defrosted, covered with
water, and simmered for about a day on low.
The next day I skim and save the fat (makes heavenly biscuits) and pull the meat from the bones. I use the meat for a chicken pie or soup. The bones and stock go back to the pot, and I add chopped onion, celery, and carrot, and half-a-cup of vinegar. Then simmer on low for two more days. The vinegar dissolves the minerals and gelatin from the bones, making the stock nutrient dense and super healthy. Lastly, it's strained and canned at 10 pounds pressure, 20 minutes for pints and 25 minutes for quarts.
As Leah said, you know you've got good stock when it cools and looks like gelatin!