Cover the chicken parts with 3½ quarts cold water in a large stainless steel stockpot and bring to a boil. When the stock comes to a full boil, reduce the heat to a low simmer and skim off the gray foam that rises to the surface. Add the onion, carrot, celery, parsley, thyme, bay, and salt. (If you plan to make a reduction, salt the stock more sparingly—it will become saltier as it reduces.) Cook gently for 3 hours, until the broth tastes rich and is a light golden color. Strain through a fine-mesh sieve or a colander lined with cheesecloth. Allow the stock to cool completely; skim the fat and promptly refrigerate. The stock is ready to use as is, or may be reduced to create a glaze or sauce.

Variation: For a brown stock, roast the chicken parts and vegetables in a 450°F, oven until nicely caramelized, about 30 minutes. Deglaze the roasting pan with a little red wine, and add a little crushed tomato to the pot.