Roux is a mixture of fat and flour used as a thickening agent in cooking. It is typically made by cooking equal parts of flour and fat, such as butter, over low heat until it reaches a desired color and flavor. The longer it cooks, the darker and more flavorful it becomes, ranging from a light blonde to a deep brown. Roux is a fundamental component in many classic dishes, especially in French cuisine. It serves as the base for sauces like béchamel and gumbo, helping to create a rich, smooth texture. Understanding how to make roux is essential for many culinary techniques.