WHAT IS A ROUX?
A roux is equal parts fat and flour, cooked on low to medium heat to help make a thickening agent or add flavor and texture to anything from soups to sauces. A roux can help add creaminess or bind fatty ingredients together. The type of fat you use depends on your preference and your recipe, but a roux is typically made with unsalted butter or a neutral oil such as vegetable or canola.
Roux is categorized by its color. There are white, blond, brown and dark brown roux, and the color is determined by the cooking time—the shortest being white and the longest being dark brown. While white and blond variations are typically used for thickening, brown and dark brown roux are generally less powerful as thickening agents and are used more for flavor.
Roux is often used in French and Cajun dishes and can also be a foundational ingredient in some Japanese curries.