Overview
Key lime pie is an American dessert pie. It is made of lime juice, egg yolks, and sweetened condensed milk. It may be served with no topping, topped with a meringue topping made from egg whites, or with whipped cream; it may be cooked in a pie crust, graham cracker crust, or no crust. The dish is named after the small Key limes, which are more aromatic than the common Persian limes, and which have yellow juice. The filling in a Key lime pie is typically yellow because of the egg yolks.
The filling is made similarly to a Magic Lemon cream pie, by simply mixing the ingredients without cooking: the proteins of the egg yolks and condensed milk and the acidic lime juice curdle, thickening the mixture without baking. Today, Key lime pies are usually baked to pasteurize the eggs and thicken the filling further.
History
Key lime pie is probably derived from the "Magic Lemon Cream Pie" published in a promotional brochure by Borden, a producer of condensed milk, in 1931. The recipe is attributed to Borden's fictional spokesperson, Jane Ellison, and includes condensed milk, lemon juice and rind, and egg yolks. It is covered with meringue, baked, and served cold. According to the pastry chef Stella Parks, users of the recipe altered it with local ingredients; she describes it as "a stunning reminder of how deeply America's traditions are shaped by advertising".
From Wikipedia (CC BY-SA 4.0).