Warm Salad of Crayfish with Cucumbers and Dill

There is some controversy regarding the cooking of crayfish—whether to bring them up to the boil from cold liquid, or just to throw them in boiling liquid. I think the latter method produces the firmest flesh, and is easier to time. If you don’t have crayfish, lobster would do, and substitute tarragon for the dill. If you use prawns and shrimp, substitute basil for dill. Do not hesitate with the butter. The recipe here is for a main luncheon dish. For a first course, halve the recipe.