Once a roux is cooked to the proper color, gradually add the liquid your recipe calls for, whisking constantly. I prefer to warm the liquid slightly first. If it's too cold, you'll spend extra time whisking while the sauce comes to a simmer. But if the liquid is too hot, the sauce may thicken so quickly that it becomes lumpy. Bring the mixture to a gentle simmer, skimming any foam or fat that rises to the surface.
Long cooking improves both the flavor and the texture of the sauce .
A roux-thickened sauce should simmer for at least 30 minutes. Stevens is a contibuting editor to Fine Cooking . Photos by Scott Phillips. Used by permission. Read our Privacy Policy .