Prepare the court bouillon. Put the whole fish into cold prepared court bouillon. (Never put large whole fish into boiling liquid. It would sear the outside of the fish, overcook it, and not allow the tissues to swell as the fish cooks from the inside out.) Bring the fish and the liquid to a boil and then reduce to a simmer. Cook the required length of time. A poissonière is the perfect pan in which to poach whole fish, but improvise if you haven’t one (p.103).
Large whole fish take about 8 minutes per pound, or judge the cooking time by the thickness of the fish. Rule of thumb is, for every inch in thickness allow 8 minutes’ cooking time. A round fish 4inches in diameter takes about 30 minutes to poach; a sole 1inch in thickness, about 10 minutes.