Like Buffalo wings and fajitas from south Texas, Key lime pie is a home-town dish that has became an American food icon. Once unique to the coral islands at the southernmost end of Route 1 in Florida, the sweet-tart, pale yellow, no-bake dessert is served in restaurants that range from deluxe steak houses to paper-napkin seafood shacks, and in variations beyond pastel custard on a graham cracker crust. Among the interesting permutations we have encountered are frozen Key lime pie on a stick from street vendors in Miami, deep-fried Key lime pie at several state fairs, Key lime milk shakes, and Key lime pie martinis.
True Key lime pie (or Key lime anything) is made from fruit dramatically different from the familiar, thick-rind Tahiti lime sold in supermarkets. The Key lime is smaller—about golf-ball size—with skin so thin that a two-fingered squeeze yields all its juice. That juice is brilliantly tart; when combined with sweetened condensed milk, its flavor creates a taste-buds balancing act of sugary opulence and citrus sourness. The truth is that many so-called Key lime pies are made not from genuine Key limes, but from the hybrid Tahiti lime. That is not an awful thing, but once you’ve tasted Key limes or an expertly made pie created from them, you will always know the difference. And you will always want pie that contains the genuine article.
Because they are too fragile to ship and store by the truckload, agribusiness wants little to do with Key limes. In the United States, they have become what residents of Florida’s Keys refer to as a dooryard fruit, so named because it grows fairly wild in people’s backyards, just outside their doors. Dependable sources for such fruit are rare and prized by cooks. Chef Doug Shook of Louie’s Backyard restaurant in Key West, where Key lime pie is made on a spicy gingersnap crust, reveals only the first name of his supplier—Doris—and says that she makes it her business to know which yards have the good Key lime trees. She gathers them and squeezes them; Louie’s uses the juice not only for pies but in an intoxicating ceviche marinade and as the sparkle in a vodka tonic.
In a genuine Key lime pie recipe, sweetened condensed milk is vital. When it first became available in the years after the American Civil War, Bahamian settlers in the Keys, having limited access to fresh dairy products, made pies with the canned milk along with juice of their native Key limes or sour oranges (another dooryard fruit), plus egg yolks for extra richness. Early in the twentieth century, Key lime groves thrived throughout the Keys, but after a 1926 Category 4 hurricane wiped them out, they were not restored or replanted. Since then, the Key lime has remained an elusive citrus legend . . . although Key Lime pie has been formally recognized as the official state pie of Florida.