Pick out the tails of the prawns, put the bodies in a stewpan with 1 blade of mace, 1/2 pint of vinegar, and the same quantity of water; stew them for 1/4 hour, and strain off the liquor. Put the fish stock or water into a stewpan; add the strained liquor, pound the prawns with the crumb of a roll moistened with a little of the soup, rub them through a tammy, and mix them by degrees with the soup; add ketchup or anchovy sauce to taste, with a little lemon-juice. When it is well cooked, put in a few picked prawns; let them get thoroughly hot, and serve. If not thick enough, put in a little butter and flour.
Seasonable at any time.
Sufficient for 8 persons.
Note: This can be thickened with tomatoes, and vermicelli served in it, which makes it a very tasteful soup.