Preheat the oven to 350°F (175°C). In a mixing bowl, combine graham cracker crumbs, sugar, and melted butter. Mix until well combined.

Press the mixture into the bottom and up the sides of a mini pie pan. Bake for 8-10 minutes until golden brown. Remove from oven and let cool.

In a mixing bowl, whisk together egg yolks, sweetened condensed milk, key lime juice, and key lime zest until smooth.

Pour the filling into the cooled crusts and bake for an additional 10-12 minutes until set. Remove from oven and let cool to room temperature.

In a mixing bowl, whip the heavy cream until soft peaks form. Add powdered sugar and vanilla extract, then continue to whip until stiff peaks form.

Top each mini pie with whipped cream before serving.