Melt the butter in a heavy saucepan. Stir in the flour and cook over low heat for 3 minutes. (This is called a roux.)
Add the milk, whisking constantly, and continue whisking until the sauce comes to a boil. Reduce the heat and simmer for 10 minutes, or until slightly thickened, stirring occasionally.
When the sauce is of the desired consistency, strain it and add the seasonings to taste.
THICKER SAUCE: Increase the butter and flour by 1 or 2 tablespoons but do not change the amount of milk.
MAKE IT LIGHT: Use a butter substitute and nonfat milk instead of the butter and whole milk.
MAKE IT AHEAD: Basic White Sauce may be stored in the refrigerator for 3 days or in the freezer for up to one month.
Yields: