Brown roux is a thickening agent made from equal parts flour and fat, typically butter, that is cooked together until it reaches a deep brown color. This cooking process develops a rich, nutty flavor, making it a key ingredient in many dishes, especially in Cajun and Creole cuisines. Brown roux is commonly used in sauces, soups, and stews, such as gumbo and etouffee. The longer it cooks, the darker and more flavorful it becomes, but it also loses some thickening power. It is essential to stir continuously to prevent burning during the cooking process.