Preheat the oven to 350°F (175°C).

In a mixing bowl, combine graham cracker crumbs, granulated sugar, and melted butter until the mixture resembles wet sand.

Press the mixture firmly into the bottoms of mini pie pans or muffin tins to form the crusts.

Bake the crusts in the preheated oven for 10 minutes or until golden brown. Remove and let cool.

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

Pour the key lime filling into the cooled crusts and spread evenly.

Refrigerate the mini pies for at least 2 hours to set.

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

Top each mini key lime pie with whipped cream before serving.