A béchamel to which cheese, usually parmesan and swiss, has been added. It's sometimes varied by the addition of fish or chicken stock or, for added richness, cream or egg yolks. Mornay sauce is served with eggs, fish, shellfish, vegetables and chicken.
From The Food Lover's Companion, Fourth edition by Sharon Tyler Herbst and Ron Herbst. Copyright © 2007, 2001, 1995, 1990 by Barron's Educational Series, Inc.