What is the primary function of the butter and flour in the Mornay Sauce method?

In the preparation of Mornay Sauce, the primary function of butter and flour is to create a white roux. This is a crucial step in the sauce-making process. The roux is formed by cooking equal parts of flour and fat (in this case, butter) over low heat until it reaches a pale color. This process helps to eliminate the raw taste of the flour and creates a stable base for the sauce.

The white roux acts as a thickening agent when liquid (such as milk) is gradually added, allowing for the smooth integration of ingredients while also preventing separation. Although the other functions mentioned, such as enhancing flavor and providing texture, may occur as a result of creating the roux, the core purpose of combining butter and flour in this context centers on thickening the sauce through the formation of the roux itself. Thus, recognizing the essential role of the roux in sauce preparation is key to understanding its functionality in a Mornay Sauce.