Mornay is a simple cheese sauce classically made with both Parmesan and Gruyère. It belongs to a family of "white" sauces that starts with a roux (butter cooked with flour). The roux helps thickens the sauce and gives it a uniform, smooth consistency. For white sauces, the roux is cooked long enough to get rid of the raw floury flavor (about 2 minutes). The roux should not brown when making a white sauce.
Mornay sauce can be served with blanched or steamed vegetables or poached or steamed fish or shellfish. It can also be used in casseroles, gratins, egg dishes, or pasta dishes.
Once you master the mechanics of making a roux, you can make other flour-thickened sauces, including béchamel or velouté. Brown sauces, such as classic American gravy, rely on a very similar technique—the roux is just cooked longer to develop color and nutty flavors.
Total Cooking Time: 20
Preparation Time: 5
Active Cooking Time: 15
Make Ahead: 2 days in refrigerator
Yield: 2 cups