Add 4 tablespoons fresh cream to ½ pint hot Béchamel Sauce. Blend well and strain through a fine sieve. Heat without boiling, season to taste with salt and white pepper, and stir in 2 to 3 tablespoons crayfish butter (shrimp or lobster butter will do) and 2 tablespoons chopped shellfish. The latter may be omitted. Wonderful with poached or coddled eggs and fish.