There's a joke in South Louisiana that every recipe starts with, "First you make a roux"—an exaggeration, to be sure, but one that's not far off in Southern and many other cuisines.
Roux thickens and adds flavor to all kinds of gravies, sauces and soups, from a creamy béchamel for lasagna to a nutty oyster stew or a dark and smoky gumbo—basically, all of the cozy foods you want to eat to ward off the lingering winter chill.
To learn roux-making magic, we turn to legendary Creole chef Leah Chase, who's been holding court in New Orleans's historic Dooky Chase's Restaurant since 1946. And, yes, many of Chase's recipes do start with a roux. "Without it, a lot of sauces would be just like water on a plate," she laughs.
Though the formula for a roux is simple—one part fat to one part flour—it's also incredibly versatile, depending on the type of fat you use and how long you cook it. To make a roux, you heat the fat, then sprinkle in the flour and constantly stir, stir, stir until it's the color you want. Almost all roux call for white flour, though Chase says you can use rice flour to make a gluten-free version.
Fat is flavor: The fat you use will affect the final flavor of your dish. Butter is excellent for white and blond roux, which form the base for béchamel or velouté. You can even use butter in a brown roux, say for an étouffée; however, do not, under any circumstances, use butter for a gumbo roux. "Never," Chase emphasizes. "It'll ruin the taste."
For gumbo, Chase uses a neutral vegetable oil, such as canola or a blend (but not olive oil). Darker roux can also be made with flavorful oils, such as peanut, which also has the benefit of a high smoke point, so you can cook it over higher heat. Even pan drippings, like bacon or duck fat, will work. (Gravy is roux based, after all.) Chase also likes to layer flavor into her roux by adding spices or fresh herbs like thyme.
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Color is everything: A roux is named for its color. The longer you cook it, the darker it will get; though the darker it becomes, the less thickening power it has. "You eventually cook all the starch out of the flour," Chase explains. For any roux, use a cast-iron or other thick-bottomed pan that conducts heat evenly. Here's a quick rundown of different roux hues:
White Roux, 2 to 4 minutes
You want white roux to be just that: Keep it over the fire only long enough to cook the flour taste out, Chase says. Usually, white roux are made with butter and used for a béchamel sauce—basically, roux mixed with milk or cream. For all butter-based roux, keep the heat low to medium, lest it scorch and force you to start over.
Blond Roux, 5 to 10 minutes
You can also use butter in a blond roux, but cook it a little longer so it reaches a lightly browned color. Blond roux is an excellent base for light gravies or cream-based soup. If you mix blond roux into stock, you get the classic velouté.
Brown Roux, 15 to 30 minutes
Brown roux adds richness and depth to any dish, though it won't thicken it as much as a lighter roux. Use this roux to thicken brown sauces like gravy, vegetable-heavy stews or étouffée, but remember: no gumbo!
Dark Brown Roux, 30 to 45 minutes
Dark roux are what give sauce picante and Cajun gumbos their deeply toasted, complex flavor. They require a lot of cooking, constant stirring and patience. Thought it helps to use oil with a higher smoke point so you can turn up the heat a little higher, there's no real shortcut to making a dark or any other kind of roux, Chase says. "Take your time and do it right," she says. "If you're in a hurry, get a sandwich."