1. Preheat your oven to 350°F (175°C). Line a muffin tin with paper liners.
2. In a medium bowl, mix the graham cracker crumbs, granulated sugar, and melted butter until well combined. Press about 1 tablespoon of the mixture into the bottom of each liner, ensuring it’s compact. Bake for 5 minutes, then let cool.
3. In a large mixing bowl, whisk together the sweetened condensed milk, key lime juice, lime zest, and egg yolks until smooth. This mixture should be creamy and slightly thickened.
4. Pour the lime mixture evenly over the cooled crusts. Bake for 12-15 minutes or until the filling is set but still slightly jiggly in the center.
5. Remove from the oven and let cool to room temperature, then refrigerate for at least 2 hours or until fully chilled. This step is crucial for the pies to set properly.
6. Just before serving, whip the heavy cream with powdered sugar and vanilla extract until soft peaks form. Top each mini pie with a dollop of whipped cream.

As you bake these pies, remember that patience is key—a lesson I learned from my grandmother, who always said that good things come to those who wait, especially in the kitchen.