Baked Stuffed Sole with Shrimp Sauce

The sauce in this recipe calls for a roux, a mixture of melted butter or oil and flour that is stirred over medium-low heat and used to thicken mixtures. Liquid is gradually whisked into the roux, and the mixture is cooked until thickened. A roux is a building block of such classic French sauces as bechamel and veloute, and it can be used to thicken soups and dessert sauces as well. In most cases, a roux is cooked for just 2 to 3 minutes to cook off the raw flour taste, and is not allowed to color, but roux used in Cajun and Creole gumbos is cooked to a range of colors, from golden to dark brown, in order to add depth of flavor.