Plan to make chicken (or other poulty) broth immediately after roasting a whole bird. I like to roast a chicken for dinner, and as each person cuts the meat off their respective bones, they put the bones back into the roasting pan (casual family dinner). After dinner, remove the roasting pan to the kitchen, and remove all the remaining meat from the carcass. If it was properly roasted, the meat should be sliding off the bones. Refrigerate or freeze the meat separately as an addition to a future soup or casserole.
Place the rest of the carcass and the drippings from the pan into a large crock pot. (Wait, aren’t those drippings just a bunch of fat? No, there’s a lot of good gelatin in there too, and don’t worry, you’ll have a chance to skim the fat off later.) Add enough purified water (3-5 qts) to cover the carcass by 1 inch (you may break up the rib cage to fit in better; a turkey carcass may need to have one half frozen for a second batch). Add 2 tsp. of apple cider vinegar; this acidifies the water and causes more leaching of minerals from the bones.
Turn the crock pot on high. After an hour or two, when you notice that the water has heated thoroughly, turn down the crock pot to low, and let slow cook for 24-48 hours. If you see skum form on the top of the broth during cooking, carefully skim away and discard. If you wish, you can add spare ends of vegetables during cooking. . . a carrot end here, extra chopped onions there. This will add richer flavor, but is unnecessary.
When the broth is finished, you should be able to easily crush a chicken drumstick bone with a spoon. Remove chicken carcass with a slotted spoon, and discard. Place a sieve over a funnel fitted into a quart size glass canning jar. Ladle broth through sieve into jar, leaving about 1.5 inches at the top. Continue to fill additional jars until all broth is stored; cover and refrigerate overnight. In the morning, you will notice a hardened white layer at the top in each jar; this is fat, and may be removed with a spoon and discarded. As you remove it, you’ll notice that the broth under it is actually Jello-like in consistency. This is caused by the minerals and gelatin which are suspended in water.
Freeze all the jars of broth which you will not use within the next 2 days. Defrost in the refrigerator 1 day prior to use.
Poultry broth is the basis for innumerable soups, or can be thickened with potato starch or wheat flour to substitute as “cream of chicken soup” in casseroles.
Update January 2013: For the last year I have been using a single lemon, halved as a substitute for the apple cider vinegar, with a more pleasing end flavor.