Wash and clean the fish, seeing that no blood remains. Place it in a fish kettle in a court-bouillon just off the boiling point; cook it slowly without boiling, and keep the kettle closed. When cooked remove part of the court-bouillon so that the fish stands dry, and steam it for a few minutes. Serve with any sauce you like, hollandaise, caper sauce, or cold with a mayonnaise, to which in this case you can add two or three fillets of anchovies chopped very fine.
Cod and other white fish with a firm flesh can be treated in the same manner.