Crust – 1 1/2 cups graham cracker crumbs (about 12 full sheets) – 1/4 cup granulated sugar – 1/2 cup unsalted butter, melted
Filling – 3 large egg yolk – 1 can (14 ounces) sweetened condensed milk – 1/2 cup key lime juice (fresh or bottled) – 1 tablespoon key lime zest (optional, for extra flavor)
Topping – 1 cup heavy whipping cream – 2 tablespoons powdered sugar – 1/2 teaspoon vanilla extract
Preheat oven to 350°F (175°C).
Mix graham cracker crumbs and sugar in a medium basin.
Mix the crumbs with melted butter until well moistened. Firmly press the mixture into the bottom and up the sides of a 9-inch pie plate to form the crust.
Bake the crust 8-10 minutes until lightly browned. Cool gently after removing from the oven while making the filling.
Whisk yolks in a medium bowl until slightly thickened. Add sweetened condensed milk and mix well.
Mix in key lime juice and zest (if using) until smooth and creamy.
Pour filling into pre-baked crust. The filling should be set but somewhat jiggly in the center after 15-20 minutes in the preheated oven.
Beat heavy whipping cream, powdered sugar, and vanilla extract until firm peaks form in a large bowl.
Spread or pipe whipped cream on cold pie. Serve: Slice and serve cooled pie. Add lime zest or thin slices for garnish.