This lovely libation, named for an ernest hemingway character who orders the very-similar jack rose cocktail, is the brainchild of new york bartender natalie jacob. Its imperative that you use a real grenadine, made from pomegranate juice (not red corn syrup, as you often find in the us). The corn stuff will do alright, but it lends the drink a sappy cotton-candy flavor that takes away from the marvelous interplay of flavors and textures.