Fontina cheese can be a good substitute for Gruyère.
The different varieties of Gruyere sauce are distinguished from one another primarily by the flavor ingredients that are added to a basic white cheese sauce. Gruyere has a subtle flavor profile and can be successfully mixed with a wide variety of other flavors, including spices, various types of alcohol, and other cheeses. While not technically a sauce, cheese fondue is also often made with Gruyère cheese.
Gruyère cheese is a soft, firm white cheese. It has a distinct flavor, but not especially strong. This flavor profile means that it can be mixed successfully with a wide variety of other ingredients without producing off-flavours.
Thick slice of Gruyère cheese.
In most cases, a Gruyère sauce is made from a simple bechamel sauce. The simplest of all sauces in traditional French cuisine consists of a roux made from butter, flour, and scalded milk. The roux and milk combine to produce a rich, creamy sauce, thanks to the butter, milk, and starch in the flour.
Cheese is often added to béchamel sauce, and Gruyère sauce is one of the most common types of sauce produced in this way. Mornay sauce is created by adding Gruyère cheese along with a mixture of other white cheeses to the basic white sauce. The resulting sauce is even richer than a plain white sauce and is infused with the flavors of the cheeses. This sauce is often modified by adding very mild flavored spices, such as white pepper or various herbs.
Mornay sauce is a type of bechamel sauce with Gruyère cheese.
Gruyère sauce meals can also make use of sauces made over broth. Gruyere melts easily and quickly and can be melted into a chicken or fish stock base to add richness and flavor to a sauce. In this type of application, Gruyère sauce is often flavored with spices appropriate to the protein with which the sauce will be served. Pepper and paprika, for example, can be added to a Gruyere sauce built on a base of chicken stock for use over roast chicken.
Baked fish and vegetables can be topped with a creamy Gruyère sauce.
Another common example of a Gruyere sauce, or something very similar to a sauce, is cheese fondue. This type of fondue is made by slowly melting cheese, typically Gruyère and some other light cheese, in a hot liquid base made up of white wine and sometimes kirsch. Mild condiments such as mustard are then added and the bread or vegetables are dipped into the fondue, which stays warm and fluffy as it is served.