There are two versions of Lobster Butter in the classical French canon.
Cold version of Lobster Butter (à froid)
1 part cooked lobster puréed with an equal amount of butter, then pressed through a sieve.
For the cooked lobster, use the coral, eggs and “creamy parts” of the lobster, cooked in a court bouillon.
It is used for cold hors d’oeuvres, cold fish and fish sauces.
Hot version of Lobster Butter (à chaud)
1 part cooked lobster puréed, blended with an equal amount of butter, then melted in a bain marie, strained through a cloth into a bowl filled with iced water. The melted, strained butter will congeal: collect it out of the water and put in on a cloth to dry.
It is used in sauces, soups and seafood stews.
For the cooked lobster, use the shell and trimmings of the lobster, either cooked in a court bouillon or in a mirepoix.