Roux is a classic French cooking technique where flour is cooked with butter to create a thickening agent for sauces and soups. It is commonly used in dishes such as gumbo, gravy, and bechamel sauce. The roux is cooked to various degrees of color from white to dark brown, depending on the desired flavor and color of the dish. The technique requires constant stirring to prevent burning and ensure a smooth consistency. Roux adds depth and richness to dishes and is a fundamental element in traditional French cuisine.