Go With Gruyere

• Mornay starts with a basic Béchamel sauce but requires some type of Swiss cheese in order to make it Mornay. Gruyere, the semi-firm cheese from Switzerland, is the traditional Swiss used in Mornay sauce. The cheese's superior taste and meltability make it the first choice for quiche, fondue and, of course, Mornay sauce. When Gruyere isn't available, other imported Swiss types, such as Emmentaler, can fill in.

Add Pep With Parmesan

• It's also traditional to include a smaller amount of Parmesan cheese in Mornay sauce. The basic balance is 1 part Parmesan to 2 parts Gruyere. This hard Italian cheese adds an extra bite to the sauce blend, as well as some saltiness. Always use hard wedges of cheese rather than convenience food shakers of pre-grated, processed Parmesan. If you can't find Parmesan, look for the similar Asiago or Romano hard cheeses.

Meet the Mother

• Mornay starts with a Béchamel sauce, the creamy white "mother" sauce. Mother sauces can be used alone or as bases for other sauces. For a basic Béchamel, develop a roux made from equal parts flour and butter, then add previously-scaled milk and aromatics such as onion, pepper and a bay leaf. When it reaches a thick consistency, strain the solids from the infused Béchamel.

Make It Mornay

• To turn a basic Béchamel into a Mornay sauce, use about 1 part of the blended cheeses to 4 parts Béchamel sauce. After you return the strained Béchamel to a saucepan over medium heat, slowly whisk in the Gruyere and the Parmesan until the cheeses completely melt and blend with the Béchamel. Once the saucepan comes off the heat, it's traditional to stir in a small amount of butter. If you need to thin the Mornay for your specific recipe, add a small amount of hot milk or broth.