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

In a clean 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, filling each mini pie to the top. Bake for an additional 10-12 minutes until set. Remove from oven and let cool.

In a mixing bowl, whip the heavy cream until soft peaks form. Gradually add powdered sugar and vanilla extract, continuing to whip until stiff peaks form.

Top each mini pie with a generous dollop of whipped cream before serving.