Parboil the lobster in boiling water well salted. Then pick out all the meat from the body and claws, and beat it in a mortar with nutmeg, mace, cayenne, and salt, to your taste. Beat the coral separately. Then put the pounded meat into a large potting can of block tin with a cover. Press it down hard, having arranged it in alternate layers of white meat and coral to give it a marbled or variegated appearance. Cover it with fresh butter, and put it into a slow oven for half an hour. When cold, take off the butter and clarify it, by putting it into a jar, which must be set in a pan of boiling water. Watch it well, and when it melts, carefully skim off the buttermilk which will rise to the top. When no more scum rises, take it off and let it stand for a few minutes to settle, and then strain it through a sieve.
Put the lobster into small potting-cans, pressing it down very hard. Pour the clarified butter over it, and secure the covers tightly.
Prawns and crabs may be potted in a similar mariner.