Melt the butter in a heavy saucepan, blend in the flour with a wooden spoon, and cook over moderate heat, stirring, until butter and flour foam together for 2 minutes without turning more than a buttery yellow color. Remove from heat, and when bubbling stops, vigorously whisk in all the hot milk at once. Bring to the boil, whisking. Simmer, stirring, for 2 minutes. Season to taste.
VELOUTÉ SAUCE. Follow the master recipe for béchamel sauce, but whisk in hot chicken or fish stock, meat juices, or vegetable broth plus milk if needed.
