This classic French thickener imparts velvety-smooth richness to soups and sauces.
What is Roux?
Roux (pronounced "roo") is a thickening agent for soups and sauces with roots dating back more than 300 years in French cuisine. Made by cooking a flour and oil paste until the raw flavor of the flour cooks out and the roux has achieved the desired color, a good roux gives dishes silky-smooth body and a nutty flavor, and thickens soups and sauces.
Home cooks usually make roux with butter, but it can also be prepared with olive oil or bacon grease! The difference between roux and other thickeners (like corn starch) is that the starch, in this case flour, is cooked before use. Cooking removes the flour's raw taste but maintains its excellent thickening properties. This makes roux a stable, smooth, and delicate thickener. Cooked to a golden or brown stage, roux takes on a rich, toasted flavor, adding color to soups and stews.
How to Make Roux
Roux takes just a few minutes to make. Whether you are making just enough for a single dish, or a batch to divide and freeze for later, the proportions of ingredients are the same: 1 part oil or fat and 1 part all-purpose flour, by weight. If you have a kitchen scale, this is easy to measure. If you do not have a kitchen scale, use measuring cups or spoons to measure 1 part oil or fat and 1-3/4 parts all-purpose flour.
We'll explain how to make a small batch.
Begin by heating 2 tablespoons oil or fat in a saucepan over medium heat until a pinch of flour sprinkled into the oil will just begin to bubble. Then, whisk in 3-1/2 tablespoons of flour to form a thick paste the consistency of cake frosting. Continue whisking as the roux gently bubbles and cooks to the shade desired. Do not allow the roux to bubble too vigorously, or it will burn rather than brown.
Whisk for Extra Smoothness in Sauce
After cooking roux, you'll usually add a liquid ingredient to make a sauce (milk added to white roux, for example, makes white sauce).
To ensure lump-free thickening when making sauces, the liquid ingredient should be cold or room temperature, and slowly whisked into the hot roux. Do this by adding the liquid a little at a time, whisking until smooth between each addition, until the roux forms a thin paste, then whisking in the remaining liquid and bringing the mixture to a simmer. Cold or room temperature roux is simply whisked into a simmering soup or sauce until it dissolves. These methods ensure the roux is incorporated slowly and the mixture will not form lumps.
Roux begins to thicken soon after it is combined with a liquid, but it must be simmered for 10 to 20 minutes in order to reach its full flavor and thickening potential. This additional cooking time allows the flour to soften and absorb the liquid, resulting in a silky smooth soup or sauce. If the simmering time is too short, the flour in the roux will remain grainy.
The Four Shades of Roux
There are four varieties of roux denoted by their colors: white, blond, brown, and dark brown. Brown and dark brown roux have more flavor, but less thickening power than white or blond roux. They are primarily used in Cajun and Creole dishes, most notably gumbo and jambalaya.
White roux is cooked for about 5 minutes, just until the flour has lost its raw smell, but before any golden color or toasted aroma develops. This roux is used to thicken chowders and milk-based sauces. Classic macaroni and cheese, tuna noodle casserole, and New England clam chowder are all based on milk thickened with a white roux.
Blond, or golden roux, is cooked approximately 20 minutes to a light, golden-brown shade with an aroma resembling popcorn or toasted bread. This is the most commonly-used roux, desired for the richness and a slight nuttiness it provides along with its excellent thickening power. Blond roux is a good, general-purpose roux to keep on hand for thickening stock-based sauces, soups, and stews.
Brown roux is cooked about 35 minutes until it reaches to a peanut butter-brown color. Its aroma is more pronounced and sharper than the nutty smell of blond roux. Cooked to this stage, flour begins to loose its thickening power, requiring more roux to thicken a given amount of liquid.
Dark Brown Roux
Even darker than the preceding brown roux, dark brown roux is cooked approximately 45 minutes until it is the color of melted milk chocolate. Its aroma is mellower than the strong, roasted flavor of brown roux, and will actually smell a little like chocolate. This stage has the least thickening power of all four; its main purpose is as a flavoring agent with thickening secondary.