In the E.B. White novel Trumpet of the Swan, a swan named Louis stays at the Ritz hotel and orders watercress sandwiches. He eats them without the bread, but since reading that book I've always associated watercress sandwiches with luxury even though it is as affordable as any other green this time of year. Somehow I got talked into buying an enormous bunch of watercress today at the market, and the first thing I made was watercress sandwiches. It might be hard to tell from the picture, but the bread is from a mini loaf (labeled 'Children's Bread'); this sandwich is a bit smaller than palm size.
Spread one slice of fluffy white bread with mayonnaise and another with butter. You can use either, but I like the combination of both. Pile very fresh, crisp, dry watercress leaves between the slices and enjoy.