You can use freshly bought vegetables, but a smarter method is to collect the normally discarded pieces of vegetables (onion and leek root, broccoli stem, celery tops, the annoying tiny pieces of garlic that are hardly worth the time to peel) in a gallon freezer bag until it's full, and make stock with that. You can do the same with chicken bones till you have enough for stock, or you can use a whole chicken and you get a nice amount of meat to use throughout the week.
Place everything in a large stockpot and add just enough water to cover it all. Cook on high heat until you begin to see bubbles break through the surface of the liquid, then turn heat down to medium low so that stock maintains low, gentle simmer.
After an hour you can remove the chicken and pick the meat off the chicken carcass. Return the carcass and remains to the stock pot and set meat aside to cool before refrigerating it for other uses.
Add hot water as needed to keep bones and vegetables submerged. Simmer uncovered for 6 to 8 hours.
Strain stock through a fine mesh strainer into a heatproof container and discard the solids. Cool immediately in large cooler of ice or a sink full of ice water to below 40 degrees. Place in refrigerator overnight. Remove solidified fat from surface of liquid and store in container with lid in refrigerator for 2 to 3 days or in freezer for up to 3 months. Prior to use, bring to boil for 2 minutes. Use as a base for soups and sauces.
