Fascinating. I made broth using backs/necks/wingtips of both the conventionally raised chicken and the pastured stewing hen. Chilled separately overnight, the fat rose to the top. Check out the difference. The fat from the Soul Food Farm hen is completely chilled, with no broth in it, but it's nearly liquid, and strikingly golden in color (with twice as much of those good Omega-3 fatty acids). The fat from the Foster Farms bird is thick and beige.

MAKING STOCK:

Making chicken stock can be as easy as covering chicken parts and vegetables with water, adding salt, and simmering for a couple of hours. But here's how I do it in detail:

If you plan on using some of the chicken for another recipe, break the chicken down into parts. You don't have to be fancy. Cut the chicken into pieces using a sharp knife and/or poultry shears. Snip the tips off the wings and put the tips in the stockpot (I usually just use  the wings in stock anyway), along with the back and neck. Leave out the giblets. They're too strongly flavored for this purpose. Reserve the breast, leg, thigh and wing pieces for your other recipe.

Use the head/feet as well, if your chicken comes with them.  Chicken feet are a tremendous natural source of glucosamine, which is extremely beneficial for your joints. They also add tons of body to the stock, giving it a rich mouthfeel without relying on fat.

If you just want to use the entire chicken for stock, you can simply put the whole bird in the stock pot without bothering to break it down into pieces.

 It's very important to add salt at the beginning, because it will help you get more flavor out of the ingredients than if you just add it at the end. I add half a teaspoon to start, if I'm just using the back/neck/wingtips from one chicken, or a teaspoon or two if I'm using a whole chicken. TIP: Do not add the aromatic vegetables yet. It's a lot easier to skim the broth without those bits floating around at the top.

Add water to cover by no more than two inches. We're going for quality here, not quantity. Bring to a simmer, with bubbles breaking the surface, but do not let the bubbles get active, and do not let it boil. Boiling will make your broth cloudy. A greyish foam will float to the surface after a few minutes. Skim this off a couple of times. When it looks clear, add your aromatics: a few diced carrots, celery sticks and an onion. The smaller the pieces, the more flavor you will extract from them.

If you have parsley stems, those are a nice addition too. I like to use several cloves of garlic. Don't use any other herbs at this point (thyme, bay leaf, etc.). We're going to simmer this for a long time, and the herbs will turn bitter. 

Things NOT to use in making basic chicken stock: any of the brassicas, such as cabbage and broccoli; onion skins; old vegetables on the verge of spoiling; green peppers; sweet potatoes. Best to stick to the classic mirepoix vegetables: carrot, celery and onion. 

Cover the pot, adjust the heat so it's at a bare simmer (a few bubbles breaking the surface every few seconds), set the timer for an hour and go about your business. Check on the water level, give it a stir to submerge parts that may have been poking out, set the timer for another hour, and go do something else. (NOTE: If you are using the whole chicken, and are not using a stewing hen, take the breast pieces out now to use in the soup later. Leaving them in longer will result in dry, tough breast meat.) 

After the second hour, check the texture of the chicken. If it's tender, I like to take the pieces out, let them cool, remove the meat and put all the bones and bits back in the pot for at least another hour. This extracts more of the collagen, improving the body of the end result.  Set your timer for another hour.

My friend who graduated from the  culinary institute lets her stock simmer overnight. I prefer to stop much sooner than that. 

When the stock tastes done to you, add more salt if it needs it, strain through a colander, put the liquid into a clean container and chill overnight. In the morning, you can scoop off most or all of the fat. A little fat left in will make the broth taste really good, and leave those wonderful little glistening flecks on the surface.

If it's a Soul Food Farms chicken, KEEP THAT EXTRA FAT! That's liquid gold. Use it instead of olive oil in your cooking (but not for high temperature cooking that will make it smoke). I put mine in a glass container with a snap-lock plastic lid, and keep it in the refrigerator.

Now you have a basic chicken stock to use in making chicken soup, to enrich sauces, as a substitute for water when making rice, or even as a hot mug of bouillon on a cold day.