Roux is a thickening agent used in Cajun cooking.

7 tablespoons vegetable oil
3/4 cup all-purpose 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.