What is the French term for a mixture of flour and fat used to thicken sauces?

The French term for a mixture of flour and fat used to thicken sauces is roux. This foundational culinary preparation is typically made by cooking equal parts by weight of flour and fat, such as butter, together over low heat until the mixture reaches a desired color, which can range from pale to dark brown, depending on the flavor profile desired for the dish. Roux serves a crucial role not only in thickening sauces but also in adding depth and richness to a variety of dishes, such as gravies, soups, and gumbos.

Béchamel is a type of sauce made with milk, butter, and flour, and it indeed starts with a roux, but it is not the term for the flour and fat mixture itself. Brunoise refers to a specific method of cutting vegetables into small dice, while emulsification is the process of mixing two ingredients that typically do not combine well, such as oil and vinegar for dressings. Understanding these distinctions helps to clarify why roux is the correct answer in this context.