Chicken Gumbo with Oysters

What survives here is the oyster finish for a chicken gumbo: the shellfish liquor goes into the pot with the vegetables, the oysters themselves only at the very end. The timing of that last step is the whole point.

• The hinge: plump, don't cookOysters need roughly one to two minutes in hot soup — just until the edges ruffle and they firm slightly. A quarter hour of simmering, which older instructions sometimes allow, turns them to rubber. Take the pot off the heat as soon as they curl.
• A quart of oystersThis means shucked oysters sold in their liquor, about 2 lb and roughly two to three dozen medium oysters depending on size, not a quart of oysters in the shell. Modern tubs are often pints; buy two, and reserve every drop of the liquid.
• Scalding the liquorBring the strained liquor just to a boil and skim off the foam that rises. This carries off shell grit and bits of mantle; left unskimmed it can leave the finished gumbo cloudy.
• StrainingA fine sieve lined with damp cheesecloth catches shell fragments that a colander lets through. Rinsing the oysters themselves in cold water, as directed, is worth doing for the same reason.
• Salt at the endOyster liquor is markedly saline and a quart of it will season the pot considerably. Hold back on salt until after the liquor has gone in and reduced with the vegetables.
• "Without the rice or rice balls"The book's other gumbos are served over boiled rice or with rice moulded into balls. This version is served as a soup on its own, so the oysters are not buried and do not sit in a hot starch that keeps cooking them.
• If the base is thickened with filePowdered sassafras leaf must be stirred in off the heat. Boiled, it turns the soup ropy and stringy, and no amount of further cooking will bring it back.
• YieldThe base recipe is not reproduced here, so any yield is guesswork; a quart of oysters is enough to finish a pot of soup for a table of several.