How to make a roux ?

Roux is a cooked mixture of wheat flour and fat, traditionally clarified butter. It is the thickening agent of three of the mother sauces of classical French cooking: sauce béchamel, sauce velouté and sauce espagnole.

Just as it is in classical French cuisine, roux is a mixture of flour and fat, usually butter or oil. The proportion is roughly 1:1, but I tend to use slightly more flour than oil; maybe 1-1/4 cups of flour to 1 cup of oil.

It is the basis for many Louisiana dishes, particularly gumbo, but also etouffees, sauce piquantes, and more.

There are three basic types of roux: light (or what the Cajuns call "blond"), medium (or "peanut butter" colored), and dark. There is white roux also, which is cooked for just a minute to get the flour taste out, but this is rarely used in Louisiana cooking. For gumbos, for instance, Creole cooks tend to prefer a blond or medium roux, where Cajun cooks tend to prefer a very dark roux, which is wonderfully smoky tasting. There are, of course, exceptions to this. In fact, you'll see people making many different "levels" of roux. Blond, light brown, medium-light brown, medium brown/"peanut butter", and dark browns that range from the color of milk chocolate to the color of bittersweet chocolate. This is the most amazing roux of all in flavor, but the most difficult to achieve; it's really easy to burn it from this point. Use your eyes and nose; if it's gone over to being burned you can smell it. It's like the difference between really dark toast and burnt toast. You also have to take it off the heat slightly before the roux gets to the color you want, because the residual heat in the pan (particularly if it's cast iron) will continue to cook the roux. This is why it's a good idea to add your "trinity" (onion, celery, bell pepper) to the roux before it gets to your desired color, because that'll help slow the cooking process.

Roux is used to thicken gumbos, sauces, étouffées or stews, and in the case of a darker roux to flavor the dish as well. Dark roux has more flavor, a wonderful roasted nutty flavor, but tends to have less thickening power.