Preparation : A few overall points may be helpful. The usual proportion of oil to flour is fifty-fifty. Roux can be made in advance, cooled, and then stored in an airtight jar for several days in the refrigerator, or at room temperature. (It keeps indefinitely if frozen). If you use a cast-iron skillet or pot (as I do) remove the roux promptly from the pot once it has cooled thoroughly; otherwise, the roux will begin picking up the flavor of the iron. If you make the roux ahead, I recommend that you don't add any vegetables to it that may be called for in recipes. Those vegetables can be omitted from the recipe or, if desired, added to the roux when it is reheated and before it is added to the finished dish. Or the vegetables can be added to the dish after stirring in the premade roux. Pour off the excess oil from the surface of the roux and reheat it (preferred); or let it return to room temperature before using. For best results, add premade roux by spoonfuls to boiling stock or liquids, stirring until the roux is blended in before adding more. A good rule of thumb for the amount of premade roux to use is as follows: Substitute the same amount of premade roux as the amount of flour called for to make the roux in the recipe. For example, if a recipe calls for making a roux with 1/3 cup of oil and 1/2 cup of flour, then substitute 1/2 cup roux for the oil and flour. As I don't normally follow recipes, but quite often make roux ahead of time, I use premade roux this way. I usually have a large margarine container in the freezer filled with roux. I usually start with a little less roux than I think the finished dish will need. Then, about 30 minutes before the dish is done, I stir in more roux, as needed, to get the flavor and consistency I want. Remember, it's always easier to add more, than it is to take out some if you put too much in. Cajun cooks view roux as being essentially of two types--medium brown and black. I actually split them up a little more than that. A blonde roux is what you start with. A little more cooking and it turns to a mahogany color, then to chestnut, finally ending up as black. I normally use a chestnut roux in most dishes. A black roux is rather tricky for a novice to make. It calls for a very high heat, continuous rapid stirring, and a quick removal from the heat just before it hits the finished black color. It is easy to burn roux, and if you do, throw it out, wash your skillet thoroughly (if it's cast iron, NEVER use soap or detergent. Just use hot water and a plastic pot scrubber) and start all over again. Traditionally, a light roux is used with dark meats, and dark roux is used with light meats. These particular combinations seem to lead to the best tasting food. In general, I use light and medium brown roux in sauces or gravies for dark, heavy meats such as beef, game like venison, and dark-meat fowl such as duck and geese. This gives a wonderful, toasted, nutty flavor to these sauces and gravies. I use dark chestnut and black roux in sauces and gravies for sweet, light, white meats such as pork, rabbit, veal, and all kinds of freshwater and saltwater fish and shellfish. Several words of advice are essential: 1. Cooked roux is called CAJUN NAPALM. Treat it with care and respect. It is extremely hot, and sticks to your skin. Be VERY CAREFUL to avoid splashing it on yourself (or others standing around you). It's best that you use a long handled metal whisk or wooden spoon. I strongly recommend that you have both a whisk and a spoon handy so you can switch them quickly if you find you're having trouble stirring with one of them.
Always begin with a very clean skillet or pot, preferably one that is heavy, such as cast iron (NEVER use a nonstick type - it doesn't withstand the heat or the constant stirring). The cast iron should be well seasoned. If possible, use a skillet or pot with flared sides (without angular corners) because this makes stirring easier and thus makes it less likely the roux will burn. In addition, use a large enough skillet or pot so that the oil does not fill it by more than one fourth its capacity. I have found that the best all-around pot for making roux is a 2 quart, cast-iron Dutch oven with flared sides. I'm also fond of using a 16 inch cast iron skillet.
The oil should be smoking hot, or just short of it, before the flour is added. (NOTE: this is different than the Justin Wilson recipe, which calls for a lower temperature and slower cooking).
Once the oil is hot, move promptly to add the flour, not only because the oil will eventually burn, but because the quality of the oil starts breaking down as it continues to heat. Stir in the flour gradually (about one third at a time) and stir or whisk quickly and CONSTANTLY to avoid burning the mixture. (flour has moisture in it, and adding it to hot oil often creates steam -- another good reason for using long-handled whisks or spoons.
If black specks appear in the roux as it cooks, it has burned; discard it (place in a heat proof container to cool before discarding), then start the roux all over again -- c'est la vie!
As soon as the roux reaches the desired color, remove it from the heat. Unless you are making the roux ahead, stir in any vegetables called for (they help to stop the browning process and enhance the taste of the finished dish), and continue stirring until the roux stops getting darker, usually about 3 minutes.
While cooking roux (bringing it to the desired color), if you feel it is darkening too fast, immediately remove it from the heat and continue whisking constantly until you have control of it; don't ever hesitate to do this. Also, lower the heat whenever you feel it is necessary.
Occasionally I have trouble with a roux not coming out just right -- that is, it "breaks" instead of dissolving when it hits hot stock or water. This doesn't happen very often, and it is always surprising and somewhat perplexing when it does. I'm not sure of the reasons why it does this, but it seems most often to be related to variations in the moisture and gluten contents of flour at different times of the year; even batches of flour with the same brand name can vary. I can nearly always tell I'm going to have a problem with a roux when I notice a blue smoke coming off the roux surface instead of the clear smoke you see when oil is just beginning to smoke. When a roux breaks, even after trying it for a second time, I find it's best to use less intense heat, or change to a different type of flour. Always try to use the highest gluten flour you can.
Care and concentration are essential for you to be successful with this fast method of making roux. Especially the first few times you make roux, be certain that any possible distractions -- including children -- are under control (I take the phone off the hook). In addition, always have all cooking utensils and required vegetables or seasoning mixtures prepared ahead of time, and near at hand before you