Filets de Maquereau au Persil

Filets de Maquereau au Persil (mackerel fillets with parsley) teaches one true thing: gentle heat protects both fish and sauce. The court-bouillon must barely tremble, because boiling tightens the mackerel before its flesh has time to turn tender. The same restraint keeps the sauce au beurre, a butter sauce, glossy rather than grainy. C'est la même grammaire.

The original kitchen assumed someone to raise the fillets, court-bouillon ready by the potful, a saucier to hand over Butter Sauce (No. 66), and a long serving dish waiting at the pass. It required neither a salamander nor a stockpot kept forever on the fire, so we won't invent them. Four prepared skin-on fillets, one wide sauté pan, and a home-scale measure of the finished sauce are the honest equivalents. Raising fish and maintaining station pots were brigade scaffolding; the parsley court-bouillon, skinning after poaching, and fresh parsley folded into the sauce at the last moment are the dish itself, and they stay.

When it is right, the mackerel remains plump beneath an ivory-gold sauce flecked vividly green, with enough sauce pooling around it for potatoes alongside. Watch the liquid once the fish goes in. If it begins to boil, lift the pan from the heat at once; ça se rattrape when you catch it promptly.