Red Colouring Butter

Beurre colorant rouge (red colouring butter) teaches one clear principle: the red-orange pigment in cooked crustacean shells moves into fat, not water. Before you touch a pan, dry the shells until they snap and grind them as finely as your tools allow; damp, leathery fragments give up little colour and trap too much butter.

The original formula assumed a saucier on staff, a mortar large enough for a day's shellfish remains, and hands available to pound and wring muslin. At home, save cleaned cooked shells in the freezer, dry one tray, crush them under a rolling pin, and finish them in a spice grinder. I have scaled the batch to 225 grams each of dried shell and butter, but kept the equal-weight ratio, the bain-marie (hot-water bath), the muslin strain, and the iced-water setting. Hand-pounding was brigade scaffolding; those four choices are the preparation itself. One cook, one stove, one evening.

The finished butter should be coral-red when melted, firm and clean when cold, with a restrained crustacean savour rather than the taste of fried shells. Keep the extraction gentle until the butter clarifies. That slow infusion is the step that decides everything.