Thin White Sauce

This is the thinnest of the standard white sauce proportions, given as a formula rather than a procedure: one tablespoon of flour to one cup of milk. It is a base for cream soups and for moistening flaked fish or vegetables, not a coating sauce.

• The ratio is the point1 tablespoon flour per cup of milk gives a sauce barely thicker than cream. In the standard scheme two tablespoons gives the medium sauce used for creamed dishes, and three to four the thick paste used to bind croquettes.
• Method, since none is givenMelt the fat, stir in the flour and cook the roux two minutes over low heat without letting it colour, then add the milk gradually off the heat or in a slow stream, whisking. Return to the heat and simmer, stirring, until it thickens.
• Cook it long enoughA thin sauce reaches its full thickness within a minute of the boil, but raw flour tastes of paste. Hold it at a bare simmer for three to five minutes, stirring, before seasoning.
• Milk temperatureCold milk added slowly to a warm roux is the most forgiving route. Hot milk works and is faster, but it sets lumps instantly if dumped in at once.
• Yield and seasoningMakes about one cup. The recipe specifies only "fat"; if you use salted butter, taste before adding all the salt.
• What to do with itThin white sauce is the body of cream soups (add an equal volume of vegetable puree or fish stock), a poaching liquid finisher, and the base for cream gravies. It will not nap a fish fillet.