If you don't have access to stewing chicken, you can substitute it with 2 broiler chickens and 1/4 cup of butter.
Place the stewing chicken, or the broiler chickens and butter, in a large, lidded stock pot. Put the pan in a cold oven and turn the temperature to 325°F. Let it slow cook in the oven for about 4 hours until it is a dark, golden in color.
Remove the pot from the oven and let it cool to room temperature. Shred the meat from the bones and return the meat and the bones to your stock pot. Fill the pot with room temperature water just until it covers the meat and bones.
Add the roughly chopped onion, bay leaf, parsley bunch and thyme bunch. Bring the water up to a simmer and let it simmer for about 10 minutes. Turn the stove off and leave the pot to sit on the cooling burner until the contents are to room temperature again.
Add another quart of water, bring the broth back up to a simmer and simmer it for twenty minutes. Strain out the chicken meat, bones and vegetables.
This recipe makes about 4 quarts of broth and will keep in the refrigerator for 4 to 5 days.