Fontina cheese can be a good substitute for Gruyere.
The different varieties of Gruyere sauce are distinguished from each other primarily by the flavor ingredients that are added to a basic white cheese sauce. Gruyere has a subtle flavor profile and can be successfully blended 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 Gruyere cheese.
Gruyere cheese is a soft, firm white cheese. It has a distinct flavor, but not especially strong. This flavor profile means it can be successfully blended with a wide variety of other ingredients without producing off-flavors.
Thick slice of Gruyere cheese.
In most cases, a gruyere sauce is made from a simple béchamel 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 are combined to produce a rich, creamy sauce, thanks to the butter, milk and starch in the flour.
Cheese is often added to a béchamel sauce, and a gruyere sauce is one of the most common types of sauce produced in this way. Mornay sauce is created by adding Gruyere cheese along with some 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 spices with very mild flavors, such as white pepper or various herbs.
Mornay sauce is a type of béchamel sauce with Gruyere cheese.
Meals with gruyere sauce 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, Gruyere sauce is usually flavored with spices appropriate for the protein with which the sauce will be served. Pepper and paprika, for example, can be added to a Gruyere sauce built on a chicken stock base for use over roasted chicken.
Baked fish and vegetables can be topped with a creamy Gruyère sauce.
Another common example of Gruyere sauce, or something very similar to a sauce, is cheese fondue. This type of fondue is prepared by slowly melting cheese, typically Gruyere and some other light cheese, in a hot liquid base made up of white wine and sometimes kirsch. Then, mild seasonings such as mustard are added and bread or vegetables are dipped into the fondue, which is kept warm and fluffy as it is served.