Roux is a cooked mixture of flour and fat used to thicken sauces, soups, stews and other preparations. It is commonly made with equal weights of flour and butter, although other fats can be used. Cooking the flour in fat coats the starch and helps it disperse when liquid is added, producing a smooth thickened sauce.
As roux cooks to a darker colour, its starch thickening power generally decreases while its toasted flavour becomes more pronounced. A darker roux therefore usually requires a different flour-to-liquid ratio than a white roux. The exact amount depends on the desired consistency, the flour, the fat and the final application.
Roux cooks flour in fat before liquid is added. A slurry mixes starch with cold liquid and is added to a hot preparation to thicken it. A slurry is quick to prepare and does not contribute the same cooked-fat flavour as a roux.
Chef’s tip: Match the roux colour to the sauce. Keep stirring as it darkens, since scorched flour creates bitterness that cannot be removed by adding more stock or seasoning.
Key distinction: Roux is a flour-and-fat thickener cooked before liquid is incorporated; it is not the same as beurre manié, which is uncooked flour kneaded into softened butter.
This term is one of hundreds covered in depth across OCS courses, learning paths, and 1-on-1 coaching with Chef Eric.
