Cheese sauce is a basic concoction, but you can customize it countless ways with various seasonings, milk products and cheeses. The richness of the final mixture depends on the milk product you add to the butter-and-flour roux. Skim or 1 percent milk yield a lighter sauce than rich and luscious half-and-half, which is best for a decadent sauce such as Alfredo. A sauce that contains only one cheese can taste great, but you can also experiment with making your own cheese blend to create a sauce that has a more complex flavor.
Melt butter in a saucepan over medium-low heat. Salted and unsalted butter are both acceptable. Margarine does not contain enough fat to contribute meaningful flavor or texture to the sauce. Stir all-purpose flour into the melted butter with a whisk or fork. Use equal volumes of butter and flour to create the roux. For example, blend 2 tablespoons butter with 2 tablespoons flour. Cook the mixture until it becomes golden, about 5 minutes. Stir constantly to prevent clumping and scorching.
Whisk milk into the mixture slowly. Add 1/2 cup of milk for every tablespoon of flour in the roux. For example, add 2 cups of milk to a roux that contains 4 tablespoons of butter and 4 tablespoons of flour. Milk with a higher fat content, such as whole milk, yields a more flavorful sauce than a low-fat alternative, such as skim. Substitute half-and-half for some or all of the milk to create a richer sauce.
It is common for the sauce to initially appear lumpy or separated when you add the milk. Water evaporates from the milk as you cook the mixture, making the sauce thicker. Stir the ingredients constantly to create a smooth texture and prevent clumping. Reduce the heat if the sauce clumps despite constant stirring. Add milk to thin the sauce if it becomes lumpy or pastelike. Stir the mixture until it is thick, smooth and even.
Add about 1/4 to 1/3 cup of grated or shredded cheese to the mixture for every cup of milk in the sauce. Stir the sauce until the cheese melts and incorporates thoroughly. Cheddar, Monterey Jack, Parmesan, Gouda, Asiago and Gruyère generally blend into sauces well. Low-fat cheese, such as mozzarella, does not blend well and yields an unalterably stringy sauce. Choose cheeses that have similar flavors or originate in the same part of the world if you create a cheese blend. For example, cheddar and Monterey Jack are a popular pair because they have similar flavors and melting points. Parmesan, Asiago and Romano cheeses, all of which are Italian, complement each other well.
Cheese does not always blend into sauce smoothly. Whisk 1 or 2 tablespoons of water into stringy cheese sauce to improve the texture. Pasta water -- water in which you have boiled pasta -- is more effective than plain water, because the starch that cooks out of the pasta helps bind the sauce. Water evaporates out of the mixture as you continue to cook the sauce, so it won’t dilute the flavor.
Season the cheese sauce to taste with salt and pepper. Use white pepper if you want to avoid the noticeable dark flecks of ground black peppercorns. Add grated nutmeg to the milk mixture to impart a subtle spiced flavor that is similar to a French béchamel sauce. Add 1 or 2 teaspoons of hot sauce or Dijon mustard to the finished sauce to intensify the flavor of a sharp cheddar mixture.