Red Bean Gumbo and roux?

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

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.

Preparation of a roux is dependent on cooking time; the longer you cook, the darker the roux. A blond roux will only take four or five minutes; a dark roux up to 20 or 25 minutes at high heat, or up to an hour at low heat. Roux must be stirred constantly to avoid burning. Constantly means not stopping to answer the phone, let the cat in, or flip the LP record over, and if you've got to go the bathroom ... hold it in or hand off your whisk or roux paddle to someone else. If you see black specks in your roux, you've burned it; throw it out and start over.

When you're stirring your roux, be very careful not to splatter any on you. It's extremely hot, and it sticks. They don't call it Creole napalm for nothing ...

Certain dishes (like crawfish étouffée) would benefit from a butter-based roux, but if you're going to make a dark roux, this will take a long time. Butter roux must be cooked at low to low-medium heat, or the butter will scorch. Darker roux are better suited to being made with oil. If you know what you're doing, you can make an oil-based roux over medium-high to high heat, whisking like hell, and you'll have a beautiful near-milk-chocolate colored roux in about 20 minutes rather than an hour. Peanut oil works best for high-heat roux cooking.