Preheat oven to 350ºF.
Make the Graham Cracker Crust: Blend the graham crackers and sugar in a food processor until it resembles sand. Add the melted butter and blend until mixed well. Firmly press the graham cracker mixture evenly into a 9-inch pie tin. Bake in the oven for 10 minutes.
Prepare the pie filling: Mix the sweetened condensed milk, sour cream, lime juice, and lime zest in a bowl. Mix until smooth and creamy. Pour the mixture into the prepared graham cracker crust.
Bake: Place the pie in the preheated oven for 10 to 12 minutes or until the tiny little bubbles burst on the top of pie. Do not let it brown when you bake it! (I bake it up to 20 min.) Chill the pie completely before serving.
(Optional) Garnish the pie: Garnish the pie with lime slices and whipped cream. In a medium-sized bowl, whip the cream, vanilla, and sugar until the cream forms stiff peaks. Add the whipped cream to the key lime pie after it has cooled completely.
