Preheat the oven to 350°F (175°C).

In a mixing bowl, combine graham cracker crumbs, granulated sugar, and melted butter. Press the mixture into the bottoms of mini pie pans.

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

Pour the filling into the prepared crusts and bake for 10 minutes. Remove from the oven and let cool.

In a separate bowl, whip the heavy cream with powdered sugar and vanilla extract until stiff peaks form.

Top each mini pie with the whipped cream mixture before serving.