Mornay sauce is a creamy cheese sauce that is a variation of béchamel sauce, one of the five mother sauces in classical French cuisine. It is made by adding grated cheese, typically Gruyère or Emmental, to a base of béchamel, which consists of milk, butter, and flour. This rich sauce is often used in dishes like macaroni and cheese or as a topping for vegetables and seafood. The origins of Mornay sauce are attributed to the 19th century, named after the Duke of Mornay. It is known for its smooth texture and savory flavor, making it a popular choice in both home cooking and gourmet restaurants. Mornay sauce can also be enhanced with additional ingredients like nutmeg or mustard for extra depth.