What is a roux used for?

A roux is a mixture of fat and flour that is cooked together and used primarily as a thickening agent in sauces, soups, and gravies. By combining equal parts of fat, usually butter, and flour, and cooking them, the roux develops a nutty flavor and a smooth texture that can be incorporated into liquid to create a thickened consistency.

When added to a liquid, the starches in the flour gelatinize and swell, which contributes to the thickening process. This principle is fundamental in classical cooking, particularly in French cuisine, where it is a key component in sauces such as béchamel and gumbo. Roux can be cooked to different degrees (blonde, brown, etc.) depending on the desired flavor and color of the final dish.

While flavoring can be a secondary benefit of using a roux, its primary function is indeed to thicken, making it an essential technique in the culinary arts.