Crawfish Butter

A classic shellfish compound butter, written in the shorthand of a cook who already knew the method. The whole point is extracting the color and flavor locked in the shells, so nothing should be discarded until it has given up its pigment.

• ProportionsNone are given. Shellfish butters of this type are generally made with a quantity of shell debris roughly equal to, or double, the weight of butter; the finished yield will be noticeably less than the butter you started with, since some is lost in the straining and washing.
• Pound it properlyThe shells must be crushed to a genuine paste, not merely cracked. A mortar is what the recipe assumes; a food processor run in long pulses does it faster, but finish in a mortar or the fragments stay coarse and hold back color.
• Double boiler, not direct heatHold it over barely simmering water until the butter is fully melted and has taken on a deep orange color. Direct heat browns the milk solids and turns the color muddy.
• "Tammy"A tammy is a fine worsted straining cloth. Use a double layer of damp cheesecloth in a fine sieve, and twist hard the last squeezings carry the most pigment.
• The ice waterStrain directly into a bowl of ice water. The butterfat sets into a soft cake on the surface while shell grit and juices sink. Lift the cake off, press out trapped water, and repeat with fresh ice water if it looks cloudy.
• "Whip it in a warmish dish"Let the cake lose its chill before beating it smooth. Cold butter breaks into shards instead of emulsifying, and the color only looks even once it has been worked.
• Keeping and usingRoll in parchment and refrigerate up to a week, or freeze for several months. It is a finishing butter stirred into bisque or sauce off the heat, spread under fish, or melted over grilled shellfish. Boiling it dulls both color and aroma.