Add graham crackers and brown sugar to a food processor and pulse until the crackers are finely ground into crumbs. Slowly pour the melted butter into the food processor while pulsing the graham cracker mixture. Continue pulsing until the mixture resembles wet sand and holds together when pressed between your fingers.
Transfer the graham cracker mixture to a 9-inch pie dish or a springform pan. Using your fingers or the bottom of a glass or measuring cup, press the mixture firmly and evenly onto the bottom and up the sides of the pan.
Transfer the pie pan to the fridge and chill for 30 minutes. To shorten the chill time, put the pie in the freezer for 15 minutes. This will help the crust set.
Whipped Cream
Pour the cold, heavy whipping cream into the chilled mixing bowl. Sprinkle the granulated sugar and pour the vanilla extract over the cream.
Start beating the cream using an electric mixer at medium speed. You can also use a stand mixer fitted with the whisk attachment. As the cream thickens, you can increase the speed to medium-high.
Keep beating until the cream thickens and soft peaks form.
Pie Filling
Add the zest of one lime to a small bowl. Juice fresh limes until you have 3/4 of a cup. About 4 limes depending upon their size.
Add condensed milk and lime juice to a mixing bowl and mix well. Fold in the whipped cream and combine all ingredients.
Add the pie filling to the graham cracker crust and chill for 30 minutes. Garnish with lime zest and lime slices.