Steeping the milk with peppercorns and a bay leaf infuses great flavor, but you can bypass that step if you choose. Try a mixture of cheddar and Swiss for a great variation on this classic sauce. In fact, almost any cheese will work.
Combine the first 3 ingredients in a medium sauce-pan, and cook over low heat 5 minutes. Remove from heat, and cool 5 minutes. Strain milk mixture through a sieve, discarding solids.
Place flour in pan; gradually add 1/4 cup milk, stirring with a whisk until blended. Cook over low heat 1 minute, stirring constantly. Add remaining milk; cook until thick (about 5 minutes), stirring constantly. Remove from heat, and add cheese, stirring until melted.