Roux

Roux is a cooking mixture of wheat flour and fat (traditionally butter). It is the thickening agent of three of the mother sauces of classical French cooking: sauce béchamel, sauce velouté and sauce espagnole. Clarified butter, vegetable oils, or lard are commonly used fats. It is used as a thickener for gravy, other sauces, soups and stews. It is typically made from equal parts of flour and fat by weight. When used in Italian food, roux is traditionally equal parts of butter and flour. In Cajun cuisine, roux is almost always made with oil instead of butter and dark brown in color, which lends much richness of flavor, albeit, less thickening power. Hungarian cuisine uses lard (in its rendered form) or—more recently—vegetable oil instead of butter for the preparation of roux (which is called rántás in Hungarian).