A cheese sauce made by using Béchamel sauce (white sauce made by cooking flour and butter and then adding milk) as the base with Swiss and Parmesan cheese added to thicken and flavor the sauce. Some recipes suggest adding fish or chicken stocks to enhance the flavor or other ingredients such as egg yolks, cream and/or butter to provide a richer flavor. Mornay sauce is commonly served over vegetables, eggs, various meats, poultry, and shellfish.