Roux is a thickening agent used in Cajun cooking.
7 tablespoons vegetable oil
3/4 cup flour
In a large cast iron skillet, heat the oil over high heat until it begins to smoke (about 4 minutes).
With a long handled metal whisk, gradually mix in flour, stirring until smooth. Continue cooking, whisking constantly until roux is a dark red brown, about 3 to 5 minutes. (Be careful not to let it scorch in the pan or splash on your skin.) Remove from heat and use as needed.
Extra roux may be kept in the refrigerator indefinitely.