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. As the liquid reduces and thickens, the pasty taste of raw flour disappears, and the sauce becomes rich tasting and velvety smooth. Molly Stevens is a contributing editor for Fine Cooking. . Used by permission. Read our Privacy Policy .