A roux, pronounced Roo, is a thickening agent made up of equal parts fat and flour. Any fat, such as oil, bacon grease, or shortening can be used, though whole butter or clarified butter are the most common. Roux is commonly used to thicken sauces, stews, soups, and gravies. A roux can be white, blond, or brown, depending on the length of time it is cooked. A darker roux has a stronger flavor, but has less thickening power. A white roux is the strongest thickener and a neutral flavor. Roux is simple to make. It can be prepared ahead of time and refrigerated until you need it.
Here’s a guide for making a small quantity of roux. You can increase the amounts, as needed, to make larger batches.
This procedure will produce a white roux. To produce a blond or brown roux, continue cooking until it begins to take on a darker color.
To thicken a liquid with your roux: A roux made with 2 Tbsp butter and 2 Tbsp flour is just about the right amount to thicken 1 cup of liquid, depending on your desired thickness. Bring your liquid to a simmer. Add some of your roux and whisk rapidly to combine. Allow it to simmer for a few minutes. The thickening power of a roux is activated by the simmering. If desired, add more roux and simmer for a few more minutes to gauge the thickness. If it’s not thick enough, add more roux. If too thick, add more liquid.