Roux is a French word and refers to a combination of a lipid (fat or oil) and flour and is a key ingredient in, probably, thousands of dishes involving some sort of sauce. Roux is the thickening agent in Mornay sauce (the basis for mac-n-cheese), brown sauce (beef or turkey gravy), and, though it isn't obvious, beef stew.
You make roux by mixing the flour with a warm lipid and then cooking it at least long enough to eliminate the raw flour flavor (about three minutes). The lipid (which can be canola oil, corn oil, lard, butter, beef fat, duck fat, even walnut oil or Crisco) coats the grains of flour and prevents them from clumping as they would if added to a hot liquid. In fact. the reason so many gravies clump is the flour is dissolved in a combination of oil and juices (water) and the juices make the flour clump. (Butter does contain water, but not enough to hurt if you whisk the flour in vigorously.)
Once the flour is well-dissolved in the oil, you whisk in liquid (broth, stock, milk, cream) and as the oil surrounding the flour granules loosens it's grip on the flour the gluten in the flour grains reach out and begins binding with the gluten in other grains - thickening the sauce. But the roux itself is just the combination of fat and flour. It simple physically, chemically, and technically - making roux is a piece of cake.
Bechamel: Basic White Sauce
- Melt 3 tablespoons of unsalted butter over medium-low heat in a saucepan until bubbly and stirring frequently to avoid burning.
- When butter is melted add 3 tablespoons of all-purpose flour and whisk to combine thoroughly.
- Meanwhile, warm two cups of milk in the microwave until barely too hot to touch (about 2 minutes on high - 125 degrees).
- Whisk in the milk, first half and as it begins thickening, another half of what remains, and then the last. Increase heat to high medium and continue cooking, whisking frequently, until it begins to bubble.
- Season with salt and pepper.
It you want a thinner sauce, reduce butter and flour to two tablespoons, for a thicker sauce increase them to 4 tablespoons. But this proportion works really well if you're making a Mornay sauce, the most common variation on Bechamel.
Mornay sauce includes cheese. It could be cheddar (as I use in my mac-n-cheese) or Gruyere as I use in my usual basic cheese soufflé. Depending on the cheese, you need one - two cups of shredded chesse. Add a teaspoon of dried mustard, perhaps a splash of Tobasco sauce or Worcestershire sauce or wine. Some fresh herbs work. Add broth or stock (such as chicken broth or turkey stock) to the roux and you have perfect, lump-free gravy.
The "take-away-point" here is a one-to-one mixture of lipid and flour, thoroughly combined and lightly cooked is a roux. Add some liquid and you have a sauce. Easy-peasy.
This roux is classical French cooking and it's purpose is thickening. The roux itself is intended to be almost tasteless. The Creole cuisines of Louisiana and the Caribbean have different ideas.
In Creole cuisines the roux may be pale and almost tasteless when it's being used in a traditional French manner, but is often cooked far longer. Paul Prudhomme writes of tan, red, mahogany, and even black rouxs. These are cooked far longer than the French version and are more often made with oil or fat rather than butter. Traditionally a Creole roux is made in a pan over medium-high to high heat on the stove-top. It requires steady stirring and as Prudhomme warns - it's Cajun napalm if you splash it on yourself. I'm too lazy and cowardly for that.
I heat the fat/oil in a pie pan in a 375 degree oven until the fat melts, whisk in the flour (same proportions as for béchamel), and then bake it, whisking every five minutes, until it's the desired color. Instead of taking 10 minutes to make a dark roux it takes 30 using this method. But it more forgiving and while it's baking I can prep the other ingredients, wash some dishes, have a beer. I'm not in a hurry or I'd be doing something far faster than gumbo of jambalaya anyway.
So here's the kicker behind Creole roux, its job isn't thickening, its flavor. The darker the roux gets the less thickening power it has and the more rich, nutty, savory flavor it contributes. Creole roux is about flavor and not thickening.
Great cooking is really about knowing your ingredients and how to make those that are made and not simply pulled from the ground or sliced from a lamb. Here is a sauce ingredient with one name, one technique, and serving two different purposes - how cool is that!