Mornay Sauce is a creamy cheese sauce that originates from France. It is made by combining a basic béchamel sauce, which is a mixture of butter, flour, and milk, with grated cheese, typically Gruyère or Emmental. This rich sauce is often used in dishes like macaroni and cheese, vegetable gratins, or as a topping for seafood. The sauce is named after the Duke of Mornay, who is said to have popularized it in the 19th century. Its smooth texture and cheesy flavor make it a favorite in many recipes, adding a delicious twist to both simple and gourmet meals.