Brush it over grilled or roasted langoustine, prawns or a fillet of white fish just before serving. A spoonful transforms a bisque, a shellfish sauce, a seafood risotto or a fish soup; a few drops lift a mayonnaise for a crab sandwich or a hollandaise for brunch eggs. It also works quietly under vegetables — grilled leeks, roasted fennel, a beurre blanc for asparagus.