About.com features a recipe for a key lime pie without condensed milk; the food blog BakedBree also has a recipe for the dessert without condensed milk that requires fewer ingredients. The About.com recipe calls for 3 egg yolks and whites to be separated, beating the yolks in a bowl.
Combine 1 1/4 cups of granulated sugar, 1/4 teaspoon of salt, 1/4 cup of flour, and 1/3 cup of corn starch into a saucepan while adding 2 cups of water, stirring constantly while the mixture thickens. Stir in about 1/3 of the mixture into the egg yolks and combine the mixture back into the pan, cooking on low heat. Stir in 1 tablespoon of butter, 1/4 cup of key lime juice, and 1 lime peel, grated. Pour the final mixture into a baked pastry shell and let it cool.
The BakedBree version of the recipe only requires 4 eggs, 1 cup of sugar, 3/4 cup of key lime juice, 1/2 cup of butter, 1 teaspoon of softened gelatin and 1 grated lime peel. Combine the sugar, eggs and lime juice into the top of a double boiler, whisking continuously over medium heat. Once thick, add the butter slowly while continuing to whisk. Add the softened gelatin and strain the mixture, removing any cooked egg pieces. Add the lime peel and pour the mixture into your chosen crust, and let the pie cool for three hours.