A rich, lemon-flavored butter sauce thickened with egg yolks. The French chef who created this sauce most likely named it for Holland because Holland was famous for butter, a main ingredient in the sauce. In addition to its use in Eggs Benedict, Hollandaise sauce is often served over asparagus or poached salmon. Many other sauces, such as Béarnaise and Mousseline, are based on Hollandaise sauce. Hollandaise sauce can curdle if even slightly overcooked, so cook it over low heat, stir it constantly, and give it close attention.