If you are using a store-bought graham cracker crust, please follow the directions on the package to pre-bake. Store-bought crusts are thinner than homemade and don't need as much time in the oven.
This filling will be enough for a standard store-bought crust. A homemade crust in a regular pie plate will hold more filling. You should be able to double the amount of filling if using a homemade crust if you want a thicker pie, in which case you will want to bake it longer, perhaps 15 minutes, for it to set.
For the Crust:
- 1 1/2 cups finely ground graham crackers (from about 9 crackers, 145 g)
- 1/4 cup butter, melted
- 3 tablespoons white granulated sugar
For the Filling:
- 1 tablespoon lime zest for filling plus 1/2 teaspoon for the topping
- 3 egg yolks
- 1 14-ounce can sweetened condensed milk
- 1/2 cup lime juice (from about 20 key limes or 4 to 6 regular limes)
For the Whipped cream:
- 3/4 cup heavy whipping cream
- 1 tablespoon powdered sugar
- 1/8 teaspoon vanilla extract
1 Make the graham cracker crust: Preheat oven to 350°F. Mix the ground graham crackers, melted butter, and sugar in a bowl.
Pour into a 9-inch pie dish and spread the graham cracker mixture with your fingers, all over the inside of the pie dish in an even layer. You can use your fingers to do this, and then use the bottom and sides of a measuring cup or drinking glass to make smooth.
Bake at 350°F for 10 minutes, then remove and set aside.
2 Make the lime filling: Put the egg yolks into a medium bowl. Using an electric mixer or whisking by hand, beat until the yolks thicken and lighten up a bit in color, about 3 minutes.
Beat in the lime zest and sweetened condensed milk for another 2 minutes.
Whisk in the lime juice until smooth.
3 Bake: Pour filling into the prepared graham cracker crust and bake at 350°F in the middle rack for only 10 minutes, until the filling is just set.
4 Chill: Remove from oven and let cool to room temperature. Chill in the refrigerator for an hour to overnight.
5 Make whipped cream topping: For a good sturdy whipped cream topping, it helps to start with a chilled bowl and very cold heavy whipping cream.
Pour the cream into a large chilled bowl. Add the powdered sugar (sifted is best) and vanilla. Use an electric mixer (or whip by hand if your gym membership ran out and you want the exercise), start on low speed and increase the speed to the highest level. Whip for several minutes until firm enough to hold shape.
Don't over-whip or you'll make butter.
Spread the whipped cream over the top of the chilled key lime pie. Sprinkle with a little more lime zest. Chill until ready to serve.