Bone stock is neither soup nor broth, but it is the base for both and can be used in the making of nearly any savory dish. An ingredient rather than a finished product, stock doesn’t taste like much on its own. And making it right is a lot more involved than boiling a leftover turkey carcass.
One of the more noteworthy non-soupy applications of stock is in the making of espagnole sauce, one of the five "mother sauces" of classic French cooking. Espagnole sauce can be mixed with yet more stock and reduced by half to make demi-glace, a rich, flavorful and altogether labor-intensive creation that is itself the base for many other sauces.
For all the prestigious places it goes, a good stock can be made from ingredients that a wino could find in a dumpster, like bones, fish heads, chicken backs and vegetable scraps. Made from mammal bones, it's called "brown stock," which is what goes into demi-glace. This is the stock that I stock up on this time of year, when I'm done stalking deer, and the venison has been cut from the bones.
Long bones, i.e. the animal's front and rear leg bones, work best, as that's where the most marrow is. To allow the marrow to melt into the stock, the bones need to be opened. Purchased bones usually come pre-cut. If you're processing meat at home, a bone saw really helps. Or do like me: wrap bones in a towel and smash them with a cast-iron skillet on the sidewalk. But that comes later.
I begin by placing the bones on a pan in the oven at 350 degrees for about an hour, stirring occasionally so they're golden brown all the way around but not burned. If you aren't in a hurry, you can also cook them longer at 300. Twenty minutes before you're done browning the bones, remove them from the oven and allow them to cool to the point where you can comfortably rub the bones with tomato paste (I use homemade ketchup). Roast for another 20 minutes, checking often to make sure the tomato paste doesn't burn.
Remove the bones from the roasting pan. Now is the time to smash them with that frying pan (or hammer) if you started with intact bones. Place the browned and broken bones in a large empty pot along with the roasting pan drippings. Put the pan on the stove over medium heat and deglaze (i.e., pour liquid into the hot pan) with wine or water, gently scraping the fond (aka the bits of goodness stuck to the bottom of the pan), assuming said fond is not burned. Never scrape a burned fond, except when cleaning the pan. Pour the deglazed pan contents into the stock pot.
Add a bay leaf, a few peppercorns, and cover everything with water. Cook very slowly at your stovetop's lowest setting, for 12 to 24 hours, maintaining full coverage of water over the bones. You don't want the stock to boil because that would make it cloudy in both appearance and taste. Try to keep the pot at the "lazy bubble" stage—the point at which a single bubble lets go from the bottom of the pot every few seconds.
Let the stock cool to room temperature, and then put it in the fridge overnight. By morning the fat will be floating on top in a solid raft that you can easily remove.
Reheat the stock back to the lazy bubble. While it's heating, prepare a mixture of equal parts celery, carrot and onion—the mixture is called a mirepoix, since we're having French class today. For two pounds of bones, use roughly a bunch of carrots, half a celery head and two onions. The veggies don't need to be cut much; indeed, larger pieces are easier to filter out, which you'll need to do when the stock is done. Carrots and celery sticks can be left whole or broken in half, and cut the onion in half. Many cooks oven-roast their mirepoix before adding it to the stock. If doing so, don't use oil or salt, and cut the vegetables into smaller chunks, which will transfer more roasted flavor to your stock.
Add the mirepoix to the stock, and cook for three more hours of lazy bubble. Strain the bones and mirepoix, and pour your finished stock into jars. Refrigerated, it will last about a week. For longer storage, freeze the stock but not in glass jars because they can crack. Or freeze smaller portions in ice-cube trays, and keep the frozen cubes in plastic bags or other storage containers. If you're stocked on stock, then whenever you want to make a little savory sumthing-sumthing, you'll be ready with your cubes.