How to make the homemade Graham Cracker Crust:Combine 1 1/2 cups graham cracker crumbs, 1/2 cup sugar and 6 Tablespoons melted butter. Transfer to a 9-inch pie pan and pat into one even layer (the bottom of a measuring cup or glass helps here). Bake the crust in a 375-degree oven for about 9 minutes.
On the top of a double boiler (I don't have one, so I use a saucepan filled halfway with water and a large metal bowl on top) combine the sugar, eggs and lime juice.
Whisk constantly over medium heat. When the mixture starts to thicken, add one piece of butter at a time. Whisk constantly until the butter has melted. Add one piece at a time until you have added all of the butter. The lime curd will be thick.
Add the softened gelatin (I sprinkle the teaspoon of gelatin over 2 Tablespoons water until it has dissolved) to the lime mixture.
Strain your lime mixture to guarantee that there are no egg pieces in your lime curd.
Add the lime zest.
Omit the lime curd ingredients - eggs, sugar, butter and gelatin.
Use 2 (14-oz) cans sweetened condensed milk and 1/2 cup sour cream mixed with the a ¾ cup key lime juice and lime zest.
Pour it into the prepared graham cracker crust and bake for 10 minutes.
Cool for 3 hours in the fridge. Finish with whipped cream and extra lime zest.