Basic Bechamel Sauce
Bechamel is the mother of all white sauces. It is named for the marquis de Bechamel, a bon vivant during the era of Louis XIV. It's used as a base for other sauces, such as Mornay, as well as a component in dishes such as gratins, Greek pastitsio, etc.
Also delicious with a bit of nutmeg grated in.