Begin by crushing approximately 2 cups of vanilla wafer cookies into fine crumbs using a food processor. In a large bowl, mix the crumbs with ¼ cup of brown sugar and ½ cup of melted unsalted butter until the mixture resembles wet sand. Press this mixture into the bottom of an 8x8 inch baking pan lined with parchment paper.

Preheat your oven to 350°F (175°C). Place the crust in the oven and bake for 13-15 minutes, or until it turns golden brown and is slightly firm to the touch. Once baked, remove the crust from the oven and allow it to cool on a wire rack for about 30 minutes.

In a medium mixing bowl, beat together 4 large egg yolks and the zest of 2 limes until pale and fluffy. Gradually whisk in one can of sweetened condensed milk, followed by ½ cup of fresh lime juice, ensuring a smooth mixture.

Pour the lime filling over the cooled crust. Spread the filling evenly across the surface.

Return the pan to the oven and bake for 15-17 minutes, until the edges are set but the center jiggles slightly. Let cool on a wire rack for another 30 minutes before refrigerating.

Refrigerate for at least 3 hours. When ready to serve, whip 1 cup of heavy whipping cream until soft peaks form and spread over the top of chilled bars.