On Thanksgiving, Carey McKearnan and her family typically squeeze more than 20 firm Key limes for the juice her mother, Sherin McKearnan, uses to make Key lime pie.
Key lime pie is eaten in Florida all year long and served every day at bakeries, restaurants and shops solely dedicated to the dessert. Even though Florida’s season for the citrus runs from June to September, bakeries are gearing up to make thousands of pies for Thanksgiving and the December holidays, especially for customers with visitors from out of town. The home cooks who prefer to make the pie at home have already stocked up on Key lime juice.
The staff at Kermit’s Key Lime Shop, in Key West, prepare to make at least 10 times as many pies as they would in an average week. For its dense pies, the shop makes its own Key lime concentrate — 800 gallons in just one day in the lead-up to Thanksgiving — and sells it in its stores as “double strength” juice.
At Keys Fisheries, a restaurant and Key lime pie producer in Marathon, workers ramp up their pie-making in the weeks before Thanksgiving, making about 1,200 a day. Many of those pies will be sold at Whole Foods Market and Wild Fork Foods. People also buy the desserts — made with a housemade graham cracker crust to evoke a taste similar to that of a speculoos cookie — from the restaurant’s retail store.
The pie was likely invented in the mid-1800s, when sweetened condensed milk was more broadly distributed, said David L. Sloan, who wrote “The Ultimate Key Lime Cookbook.” Mr. Sloan said fishermen likely combined that milk with Key limes, stale bread and wild bird or turtle eggs to make the first versions of the pie. In 1919 and in 1926, he said, the pie appeared in restaurant ads.
But in researching her book “BraveTart: Iconic American Desserts,” which included a Key lime pie recipe, Stella Parks said the first reference she found to bakers’ combining condensed milk and citrus to make pie was in a 1931 Borden ad for a Magic Lemon Cream Pie. The first printed reference to Key lime pie that she discovered was published in 1941 in a food service magazine.
Ms. Parks said she thinks that Borden originated the technique and that Floridians adapted the recipe with Key limes. “Of course, we’re all one dusty vintage cookbook away from discovering new bits of American history,” she said.
Today, the pie is a staple for Floridians. Derek Kaplan, a former Miami firefighter, developed his Key lime pie when he was a teenager, testing it several times before he felt he nailed the recipe.
At his bakery, Fireman Derek’s, the Key lime pie is the signature item, and he includes it on his Thanksgiving preorder menu. Out of the 10,000 pies his staff will sell at his three locations, at least 1,500 are Key lime.
“Key lime pie is a no-brainer in Miami,” said Mr. Kaplan, who added that this pie is his favorite. “It’s very simple, and you don’t have to put a lot on it to enhance it. It comes in an amazing form and flavor.”