Most simply, a gravy is any thickened cooking liquid. Saurbraten, for example, is served with a gravy made from its braising liquid thickened with gingersnap crumbs. Pan gravy, however, is gravy made from, and served with, a roast. As roasting is a dry cooking method, and the roast should never be covered, the process becomes somewhat complex. However, taking each step at a time, a great pan gravy is within any cook's reach.
There are five steps to making good pan gravy:
Each step has it's specific function.
First, you want to consider what a good gravy is. It is not just a sauce to pour on sliced meat, or turkey, or mashed potatoes. It is a sauce that has the essential flavors of the roast in it. If your roast is studded with slivered garlic and rosemary, and coated with kosher salt and cracked pepper, then all those flavors, along with the meat, should be present in the gravy. You want to use a gravy to recover from the roasting pan these elements which would be otherwise lost. Therefore, the key to good gravy is recovery of essential flavors.
Also, before you make your gravy, think of how much you will be wanting. For a roast chicken serving four people, you might want two cups. (Better too much than too little). For a small roast turkey, twice that. For a large roast turkey, a quart or more. For each two cups of gravy you will need two cups of liquid -- stock, broth, water or milk -- and one tablespoon of flour. (For thicker gravy, use more flour.) The best liquid is a stock or broth made from the same kind of food as your roast -- chicken stock for chicken, turkey broth for turkey, a beef stock for a roast beef. Milk can be used for a "cream gravy" for poultry. Water should be used only when nothing else is available.
First, remove the roast from it's roasting pan and place the pan, with the drippings in it, on a burner (or two burners) over low to medium low heat. (Don't use a foil roasting pan). Cook, stirring the pan, until the juices come to a boil. Continue to cook, lifting particles off the pan, until the liquids boil away leaving a clear fat. (You should know when this happens by the clarification of the liquid, and the change of the sound from a hissing to a sizzling.) As the fat begins to heat, the proteins (blood) in the drippings will begin to caramelize, turning a dark brown color.
Remember,the whole purpose of caramelizing the liquid is to concentrate the flavor of the roast into an essence.
Carefully pour off the fat into a measuring cup, making sure to leave as much of the caramelized bits in the pan as you can. Fat into a measuring cup, solids in the pan. You may leave a small amount of grease in the pan to keep the caramelized bits. Reserve the clarified fat.
To the hot pan with the caramelized bits in it, add the liquid. Stir to loosen and dissolve any cooked-on residue while you bring the liquid to a gentle simmer.
The best thickener for gravy is a roux. For maximum flavor, make your roux with the clarified fat reserved in the "degrease" stage. For each two cups of liquid use a tablespoon of fat. Heat the fat over medium heat in the bottom of a clean saucepan. Add the flour and stir and cook for a minute. Pour in the liquid (which now has the caramelized essenses of the roast dissolved in it) into the roux and bring to a boil, stirring constantly.
Season to taste with salt and pepper. I have found that gravy takes a lot of salt, probably because of the high fat content.
I want to make pan gravy to accompany for a chicken I have roasted. After taking a roast chicken from the oven, I put the roasting pan on a burner and cook it until the water boils off. Pour off the fat and add a pint of hot chicken stock. Stir, scraping, until the stock boils. Set aside. In a clean pan I make a roux, using the chicken fat poured off earlier, then stir in the enriched stock. Season to taste.
However, things are not always so simple. All the above assumes that you have a roasting pan you can cook in, and plenty of stock on hand. Obviously, this is not always the case.
Recently I was asked to make a gravy from a turkey which had been cooked, mostly covered, for a very long period of time. The turkey had more or less collapsed around its skeleton, and because it had been covered, sat in it's liquid to a depth of two inches or so. There was no other stock, or broth, and the pan was such I could not cook in it.
First, I knew I had to use the "broth" of pan juices from the pan as the liquid for the gravy. Therefore, I completely skipped the caramelize/deglaze steps. Instead, I poured off the liquid, a mixture of broth and fat. I estimated there to be about a quart. I let it sit long enough for the fat to collect at the top, then skimmed that off.
I measured four tablespoons and clarified it in a saucepot. When it was almost smoking, I stirred in three tablespoons of flour and cooked that long enough for the color to begin to change. I then poured in the pan broth and brought it to a simmer. I corrected the seasoning and was done.
Then, however, I realized that the amount of gravy was inadequate for the size of the group. (There were seventeen people.) So, I needed to stretch the gravy. I poured the gravy into a nearby bowl, cleaned the pot, and heated some butter in the pan and made more roux. (I had by this time discarded the skimmed turkey fat, which was a mistake.) I added milk to the roux and made fat white sauce. I added the gravy to the while sauce. It was more pale, and I had to add a little more salt and pepper, but it was otherwise quite good.