Preheat your oven to 350°F (175°C). Crush the vanilla wafer cookies into fine crumbs using a food processor or a rolling pin.

In a bowl, combine the crumbs with brown sugar and melted unsalted butter until the mixture resembles wet sand. Press this mixture firmly into the bottom of an 8x8 inch pan.

Bake for 13-15 minutes until golden, then cool for 30 minutes on a wire rack.

While the crust cools, whisk together the egg yolks and fresh lime zest in a medium bowl until well combined. Gradually add the sweetened condensed milk and mix thoroughly.

Pour in the fresh lime juice, whisking until the filling is light green and fully blended.

Once the crust is cooled, pour the filling over it and spread it evenly. Bake for 15-17 minutes.

Remove from the oven and cool on a wire rack for another 30 minutes.

Once cooled, cover and refrigerate for at least 3 hours. Whip the heavy cream until soft peaks form.

Spread the whipped cream over the set Key Lime Pie Bars, slice into squares and serve cold.