Roux as a Thickener

A cornerstone of sauce making, roux is made by cooking flour and fat together until they form a paste. Roux is used primarily as a thickener, but it also adds complex flavor to whatever dish it's used in. When making roux, begin by heating the fat in a heavy saucepan. Butter is used most often, but roux can also be made with vegetable oil, lard or duck fat. Once the fat has melted, add an equal amount of flour and stir until smooth. Cook the roux over medium-low heat, stirring constantly, until it has reached the desired color.

Roux can also be made for thickening but not for adding color or flavor. Cook the roux for only a few minutes without letting it color which is also known as white roux. However, to make roux for thickening and adding a light color and flavor, cook the roux until it turns golden blond in color. Use this type of roux to enrich cream-based soups and sauces.

To make a roux with a complex flavor but little thickening ability, cook the roux until it turns dark brown. This is the most flavorful roux, but keep in mind that a roux loses its thickening power as it cooks. Dark roux is a traditional ingredient in Cajun gumbo (which gets extra thickening from cooked okra).

Make sure that any added liquid is not steaming hot. If it is, the sauce will thicken too quickly and become lumpy. Cook the sauce at least 30 minutes before serving to eliminate any raw flour taste in a roux-thickened sauce. If you need to cook a brown roux faster, toast the flour first. Heat a small skillet over medium-high heat. Add 2 tablespoons flour to the hot, dry skillet and stir until the flour turns light brown (1 minute) or dark brown (2 minutes). Stir constantly to ensure that the flour doesn't burn. Remove the skillet from the heat and stir in 2 tablespoons butter or margarine until melted. Makes enough to thicken 2 cups liquid.