Pick the meat from the tails of twelve boiled crawfish; dry the shells, and pound them all together in a mortar, adding one ounce of good butter; then place it in a saucepan on a moderate fire, stirring, until it clarifies, for about five minutes; then strain through a napkin, letting it drop into cold water. When it is congealed, take it out, and place it in a warm basin, stirring until it assumes the desired color. The same method can be used for lobsters and shrimps.