Basic Béchamel (White) Sauce
A classic French recipe, this creamy sauce thickened with a roux can be used as a base for many other sauces as well as in casseroles and soufflés.
Heat butter or oil in large saucepan over medium heat. Whisk in flour, and cook 2 to 3 minutes, stirring or whisking constantly. Gradually whisk in milk, and cook 5 minutes, or until sauce has thickened, stirring or whisking constantly.