Dry the fillets thoroughly and cut into four pieces. Season lightly on both sides with salt, pepper and lemon juice. Prepare the lettuce leaves by draping them over a large colander, and gently pouring boiling water over them to blanch them. Cool under cold running water, and dry carefully on kitchen paper. Cut out any central ribs that still remain firm and that would make it difficult to roll the leaves. Lay three leaves on the worktop, overlapping slightly. Put a mint leaf in the centre, a fish fillet on top and another mint leaf on top of the fish. Fold the lettuce leaves around the fish, enclosing it completely. Do the same with the remaining fish and lettuce leaves, and place the parcels in a steamer basket. Bring a saucepan or steamer of water to the boil, put in the rest of the mint sprigs, and place the steamer above the water level. Cover tightly and steam for 5–8 minutes, depending on the thickness of the fillets.
To make a sauce to serve with the fish, boil up the stock and vermouth until reduced to a few spoonfuls of shiny syrup. Whisk in the butter, one piece at a time, and pour a little sauce on to each heated dinner plate, alongside the fish parcel.
Omit the mint, and sprinkle the pieces of fish fillet with a little diced tomato and finely chopped shallot before wrapping them in the lettuce leaves. For the sauce, omit the vermouth, and boil up the fish stock with a little of the juice from the diced tomato. Then stir in some saffron liquor, which is prepared by soaking a pinch of saffron threads in a little hot water or fish stock, and season to taste.
© 1995 Frances Bissell. All rights reserved.