Preheat the oven to 375℉.
In a mixing bowl combine the graham cracker crumbs, salt, and brown sugar.
Melt the butter in a small saucepan, and add it to the graham cracker crumb mixture. Mix well to combine.
Press the graham cracker crumb mixture evenly into a pie pan. Place in the oven to bake for 8 minutes. Remove and set aside.
Turn the oven down to 350℉.
In a mixing bowl whisk together the egg yolks and sweetened condensed milk.
Add the key lime juice and fresh lime zest and whisk to combine.
Pour the filling into the prepared graham cracker crust and using a rubber spatula scrape the bowl clean and even out the filling.
Place the prepared pie on a baking sheet pan and place in the center rack of the oven. Bake for 11 minutes at 350℉.
Remove from the oven, and cool completely in the refrigerator for 1-2 hours.
While the pie cools down, add the heavy whipping cream and icing sugar to the bowl of a stand mixer and whip on low speed increasing to high until it's light and fluffy (whipped cream consistency).
Fill the pastry bag fitted with a star tip and pipe whipped cream on the cooled pie. Use sliced lime and lime zest to garnish, slice and enjoy!