Maquereau Bouilli, Sauce aux Groseilles

Maquereau bouilli, sauce aux groseilles (poached mackerel with green gooseberry sauce) teaches one clean principle: rich fish needs bright acidity, and neither the vinegar nor the tart fruit should be softened into politeness. The fish must poach at a bare tremble. Let the liquid boil and the flesh tightens, the skin splits, and the beautiful cross-cut pieces begin to break.

The original assumed a full five-quart batch of Court-bouillon with Vinegar (No. 163) waiting for service, a saucier tending gooseberries in a copper sugar boiler, and another pair of hands watching the fish. One cook makes the sauce first and holds it warm, then uses a snug shallow pot, a small nonreactive saucepan, a clean towel, and a fine-mesh sieve. The gooseberries and sugar are reduced to half the book's quantity while preserving its three-ounces-to-one-pound ratio exactly. The copper boiler, tammy, and brigade basin were scaffolding; the acidulated poach, fennel, green fruit, and smooth sieving are the dish and must stay.

What reaches the table is wonderfully direct: pale, moist mackerel surrounded by crisp curled parsley, with a muted green sauce that tastes tart first and gently sweet second. If the sauce is too loose or too stiff, ça se rattrape, but give your full attention to the poach. Holding that court-bouillon below a boil is the step that decides the dish.