Preheat Oven: Set to 350°F (175°C).
Make the Crust:
In a medium bowl, combine graham cracker crumbs, sugar, and melted butter.
Press mixture firmly into the bottom and up the sides of a 9-inch pie dish.
Bake for 8–10 minutes until lightly golden. Remove and let cool slightly.
Prepare the Filling:
In a mixing bowl, beat egg yolks with an electric mixer for 2 minutes until thickened.
Add sweetened condensed milk and beat for 2 more minutes.
Stir in key lime juice and zest until fully combined.
Bake the Pie:
Pour filling into the crust and smooth the top.
Bake for 15 minutes, or until the center is just set (it will jiggle slightly).
Cool and Chill:
Let pie cool to room temperature, then refrigerate for at least 3 hours, or overnight for best flavor.
Make the Whipped Cream:
In a chilled mixing bowl, beat heavy cream, powdered sugar, and vanilla until soft peaks form.
Assemble & Serve:
Spread or pipe whipped cream over the chilled pie.
Garnish with extra lime zest or slices if desired. Slice and enjoy!