Preheat oven to 350°.
Make the filling: Whisk the lime zest and egg yolks together in a medium bowl for 2 minutes. Whisk in the sweetened condensed milk, then the lime juice. Set aside at room temperature to thicken while you prepare the crust.
Make the crust: In a medium bowl, stir together the graham cracker crumbs, brown sugar and salt – ensuring no lumps of brown sugar remain. Drizzle the melted butter over the graham cracker mixture and toss to combine with a fork, ensuring the mixture is evenly moistened. Press the crust mixture into the bottom up the sides of a 9” pie plate, and pack tightly using the bottom of a measuring cup. Bake for 10 minutes at 350°. Let cool on a wire rack for 10 minutes.
Once the crust has cooled to room temperature, pour the lime filling into the crust. Bake at 350° until the center is set, yet still wiggly when jiggled, 15 to 17 minutes. Return the pie to the wire rack and cool to room temperature. Refrigerate for 3 hours minimum. At this point you can cover with plastic wrap until ready to serve – up to a day.
Make the whipped cream: Whip the cream on medium speed until soft peaks form. Slowly add the powdered sugar while continuing to whip. Stiff peaks should form. Pipe the cream onto the pie and garnish with lime slices.