Our popular Kitchen Geekery column is back! And this time our resident baking and cooking science expert, Dr. J, addresses all your burning questions about making gravy.
Many of us like to serve our holiday meals and Sunday roasts with a gravy boat filled with — you guessed it — homemade gravy. And while the science of gravy seem a little complex, making a gravy is nothing to sweat over, really. Here’s what you need to know about gravy.
The Basic Formula of Most Gravies
Most gravy recipes begin with a roux. A roux is usually made with equal parts of fat (whether the drippings from a Sunday roast or butter) and flour. The ratio of flour to liquid can vary depending on the recipe. The liquid can be anything from water to homemade stock (even vegetable stock). Obviously, the more flavourful the liquid, the more flavourful the gravy. You could summarize the basics of gravy-making as follows:
In other words, if you start with 1 tablespoon of fat from your Sunday roast, add 1 tablespoon of flour; then, once the roux is cooked, you'll need approximately 120 mL (1/2 cup) of broth or stock to make gravy. Bring that mixture to a boil, whisking constantly, and the gravy will transform from a fluid liquid to a thick, velvety sauce.
The order of addition of each component of gravy is crucial for success, as is the heat. For example, if you add the flour to the liquid at the end, instead of at the beginning of the gravy-making process, you'll have a lumpy mess on your hands and a sauce that won't thicken properly. And if you don't cook the roux before adding the liquid, your gravy will lack a certain depth of flavour that comes from the browning of the roux at the beginning of the process. Bringing the gravy to a boil is also key for the gravy to thicken properly. Really, gravy made without heat is more of a flour slurry than a real sauce that can coat the back of the spoon. So, if your stove is broken, gravy is NOT what you should be making for dinner.
How Does Flour Thicken Gravy?
The thickening process of gravy has two major steps: swelling and gelling. When heated, the starch granules in flour absorb water and swell. And these swollen starch molecules make it very hard for water to move around them and circulate, so the water becomes less fluid. Essentially when the starch swells, the water (or broth) is thicker. Eventually, the swollen beads of starch spring a leak, and strands of starch flow out of the starch granules and into the liquid of the gravy, forming a network, trapping water. The sauce gels.
How Can You Rescue A Gravy if You’ve Added Too Much Liquid?
Sometimes, you might find that after you bring your gravy to a boil, it doesn’t thicken as much as you would like, either because you didn’t start with enough flour or because you added too much liquid at the end. Don’t panic! There's a great kitchen hack to thicken a gravy that's too liquidy: beurre manié.
Beurre manié is a paste formed by kneading together equal parts flour and softened butter. Take a knob of this paste and add it to your loose gravy. The butter will slowly melt into the sauce, releasing the flour into the gravy in a more controlled fashion, allowing it to slowly do its job of swelling and gelling, without clumping the way flour would were you to directly toss some into the gravy. Beurre manié is a good trick to have for rescuing gravy.
There's no reason to fear gravy (nor to opt for a grocery store substitute that comes in a pouch). If you follow the steps in the right order, with a little whisking and heat (and a beurre manié up your sleeve, just in case), it's all gravy! Literally!
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Kitchen Geekery is written by Janice Lawandi. Janice is a PhD-chemist-turned-baker, which is why she loves to use science to understand and solve problems in the kitchen. She’s currently working as a recipe developer and food photographer in Montreal, QC. Visit Janice’s blog, Kitchen Heals Soul, for more baking science and inspiration. You can also follow her on Facebook, Twitter, and Instagram.