Lay pieces of firm-fleshed white fish and lemon slices on the beans. Use cod fillets or cod loin, haddock, flounder, or hake; try to buy pieces of similar thickness so they cook evenly.
In fact, any fresh fish fillets—the fresher the better—can be cooked this way. I like to buy cod loin fillets, which are the thick ones from the back of the fish. About 1 inch thick, they will need 5 ...