Bechamel Sauce (White Sauce)

It's from the "Joy of Cooking" by Rombauer, Becker, and Becker, 75th anniversary edition.

This is a basic sauce, which is unassertive and smooth, and can be used as the base for many other sauces. Make the sauce a bit thicker than you think you need, since its easy to thin, but hard to make thicker. To think, just whisk a bit of milk into the sauce.

1 Tbsp butter
1 Tbsp flour
1/2 cup to 1 cup milk
salt
pepper (preferably white)

Melt butter in a saute pan. Make a roux, by adding flour, and whisk until smooth (about 1 or 2 minutes). Remove from heat, and slowly whisk in the milk, until it is just a bit thicker than you'd like. Return the pan to heat, and continue to whisk while it cooks for 1 or 2 minutes, and the sauce is smooth and thick. If the sauce is too thick, continue whisking in a bit of milk. Season with salt and pepper, and grated nutmeg.

The Joy also suggests that scaled milk can be used instead of cold milk to get an even better consistency.