Well the short and simple answer to the titular question can be found right here. Store-bought gravies just don't taste right. Sure, some of them have that nostalgic cafeteria appeal, but unless you're seriously trying to relive middle school, you're much better off making your own. With a few store-bought staples, it's surprisingly easy, and worlds better than anything you'd get out of a jar.
The gravy recipe attached to this article is dead simple and will get you results that are a marked improvement over store-bought. If you want to up the ante even more, just follow these tips. They apply to any and all gravy:
You Don't Need to Make Your Own Stock
Sure, in an ideal world, if you had the time and inclination, making your own stock by browning the chopped carcass and neck of your turkey and simmering it with lots of vegetables is really the best way to make your gravy. But a good quality low-sodium store-bought chicken stock makes a flavorful base that's far better than jarred gravy (see our tasting results). Even if you are planning on using your turkey neck and scraps (highly recommended!), use stock to simmer them instead of water for an instant flavor-boost.
Make Your Gravy in Advance!
Gravy can be made at least a few days before thanksgiving. Get your turkey ahead of time, and you'll even have a neck and giblets to work with. Make your gravy on Monday or Tuesday, refrigerate it, then don't even think about it until turkey day. It'll reheat well in a small saucepan, or just in the microwave (stir it every 30 seconds while microwaving to make sure it doesn't explode).
Reach for the Umami-Bombs
Marmite and soy sauce might seem like odd ingredients for gravy, but when used judiciously, they can seriously increase flavor, adding depth and savoriness. A quarter teaspoon of Marmite and a teaspoon of soy sauce for every quart of gravy is about the right amount.
If going the store-bought stock route, try simmering it down with a couple of bay leaves, peppercorns, and some fresh herbs like thyme or parsley stems. You'll be amazed at the depth of flavor it picks up with just a quick 30 minute simmer.
Deglaze Your Roasting Pan
Your turkey gives off plenty of flavorful liquids and solids while its roasting. Look at the bottom of the pan when the turkey is done—see the browned bits in there? That's called fond, and is an instant gravy-booster. While your turkey is resting, place your roasting pan over a burner and pour in some stock. Scrape up the browned bits with a wooden spoon, strain, and use this enhanced stock as the base for your gravy. Even if you make your gravy in advance, you can always give it a boost last minute by deglazing the pan with a little stock and whisking it into your gravy just before serving.
Thicken the Right Way
To thicken a quart of gravy, melt 4 tablespoons of butter over medium heat in a medium skillet. Add 4 tablespoons (1/4 cup) of flour and cook it down, stirring constantly with a wooden spoon. You're going for a nice golden-blond color, which will add some nuttiness. Slowly add your stock, whisking constantly. The harder you whisk and slower you add the stock, the smoother your gravy will be. Once you've added all the liquid, bring it up to a boil, reduce it to a simmer, and let it cook down until it gets to the right consistency. Season it at the end with salt and pepper (seasoning too early can lead to the salt concentrating and becoming too strong).