To make a roux, you combine animal fat with flour, then whisk those ingredients until the combo takes on the particular color you are after, which can range from light blond to deep, dark chocolate. After that, you mix it in with soups, stews, and sauces to thicken them up. It’s easy enough to get right as long as you just keep whisking. Stop whisking, however, and your roux will be instantly at risk of burning. Once you see those little brown bits, the gig is up—you have to toss the whole thing out and start over