Steaming is a rapid way to cook fish and is especially appropriate for thin fillets, which can cook through quickly (thick pieces would overcook on the surface while their interior cooks through). Subtle aromas are contributed by herbs and spices, vegetables, and even seaweed, if they’re included in the steaming water or provide a bed on which the fish sits.
Even cooking requires that the fish pieces be the same thickness, and that the steam have equal access to all surfaces. If fillets taper down to a very thin end, fold the thin layers over or interleave them with each other. More than one layer’s worth of fish should be cooked in batches or divided among separate levels (as in stackable Chinese bamboo steamers). Relatively thick steaks or whole fish are best steamed below the boil, at an effective temperature of 180°F/80°C, to minimize overcooking of the surface. This can be achieved by lowering the heat on the pot and/or leaving the pot lid ajar. An even gentler effect is achieved by the Chinese method of steaming fish without a lid, in which steam and room air combine to give an effective cooking temperature of 150–160°F/65–70°C.