How to make a roux, the best sauce thickener and flavor booster you'll ever try

• Roux is flour and fat cooked together until it reaches a color ranging from a pale golden to dark brown.
• Roux is often used as a thickener for sauces and soups, and as a flavor booster for stews.
• To make a proper roux, take your time, stir continuously, and keep a close eye on the color.

One of the most classic ways to add unforgettable texture to a soup or a sauce involves adding a roux, a French cooking staple that's made with equal parts fat and flour. Both ingredients bolster the thickness of the soup or sauce, giving it a sturdy backbone and plenty of stage presence.

In the world of classic French cooking, roux is made by whisking or stirring together equal parts flour and butter. However, fans of Cajun and Creole cuisine (like jambalaya, etouffee, and gumbo) may be more familiar with the Louisiana version of roux, which replaces the butter with oil in order to achieve a deeper color and flavor.

Whether you're using butter, oil, or even bacon grease, a strong whisking arm and plenty of patience will result in a perfect roux to serve as the base for your next hearty winter soup or finishing sauce. Brandon Boudet, New Orleans native and co-owner and executive chef of Little Dom's in Los Angeles, provides his insight on how to achieve the perfect roux for any kind of dish.

Choose your roux

The color of a roux deepens and darkens the longer it cooks, and how you plan to use your roux will dictate the roux color you'll need. If you mainly want the roux as a sauce thickener or for gravies and cream sauces, a white or blond roux will serve that purpose best. But if you want to get some deep, intense flavor notes out of your roux, then a dark version will deliver.

Each roux type takes a certain amount of time to achieve, and each will develop varying thickening or flavoring properties as it cooks.

Quick Tip: It's possible to make a roux that's gluten-free by using rice flour or cassava flour instead of all-purpose flour.

How to make a roux

A proper roux doesn't involve any shortcuts, so Boudet says you'll need to "take your time and stir constantly."

1. Start with equal parts of flour and fat. If you're making a white or blond roux, butter is the ideal fat to use. If you're going for a brown or dark roux, try oil. Vegetable oil, canola oil, grapeseed oil, and peanut oil are all viable options. Always make more than you think you'll need; since roux is a time-consuming process, it's always better to over-prepare than to realize that you didn't make enough.
2. Put the flour and the fat in a heavy-bottomed pot over medium-low heat. "Use a wooden spoon to stir the fat into the flour, continuing to stir until well incorporated," says Boudet. Some chefs prefer to use a whisk for this process, but either tool works.
3. While the roux is coming together, stir every 15 to 30 seconds. "To prevent [the] roux from forming lumps, the key is to mix constantly in the beginning," Boudet says. The early phase of cooking (the "white roux" phase) is the most crucial time for constant stirring, but Boudet points out that the stirring shouldn't stop until you've reached the darkness level you want.
4. Cook your roux to its desired color level. Keep a close eye on the color, as that will be the truest indicator of where your roux is on the darkness spectrum. And remember: don't stop stirring throughout the cooking process.

Quick tip: If your roux smells like burnt toast (not nicely browned toast, but fully overdone toast), then you've probably burned it. Another telltale sign of burnt roux is the sight of tiny black specks floating around. Boudet doesn't recommend trying to salvage a burnt roux - you're better off just starting over.

How to store roux

If you find yourself with extra roux, Boudet says you can store it in a plastic container with a lid in the refrigerator for five to seven days. To revive your refrigerated roux, Boudet says to "bring the roux back up to temperature in a pot, then add some of the preferred heated liquid [whatever fat you used to make the roux], whisking it in slowly until it reaches the desired thickness."

Insider's takeaway

Roux isn't a difficult cooking project, but it definitely can't be rushed. There are four types of roux you can make depending on how long you cook it for. The kind you make will vary depending on if you need a thickener, or something to add flavor to a dish. As long as you've got a limber arm for stirring and a sharp eye to focus on the color of your fat-flour mixture, you'll be ready to make this classic mixture.