1. To make crust: Combine cookie crumbs and melted butter in a small bowl and stir until the cookie crumbs are evenly moistened. Press the crumb mixture evenly into a 9-inch pie plate, making sure the crust goes all the way up the sides. Freeze for at least 2 hours.
2. Pour the apple cider into a small bowl and sprinkle the gelatin on top. Set aside.
3. In a large saucepan over medium heat add the brown sugar, pumpkin pie spice, kosher salt, milk, egg yolks, and pumpkin. Whisk this mixture continuously over medium heat for about 10 minutes; do not let it some to a simmer or boil. Remove the pan from the heat and stir in the cider mixture, whisking until the gelatin has completely dissolved.
4. Pour the mixture into a large bowl and allow to cool to room temperature for about 15 minutes. Then place it in the refrigerator until chilled, about 1 hour.
5. Using an electric mixer, beat the egg whites and confectioners' sugar until stiff peaks form. Stir of the egg whites into the chilled pumpkin mixture. Then, use a spatula to gently fold in the remaining egg whites just until white streaks are no longer visible.
6. Pour the pie filling into the frozen crust and refrigerate for at least four hours, or until the filling is set.
7. To make the topping: Whip together the confectioners sugar and cream until soft peaks form. Spread the cream on top of the chilled pie. Slice and serve immediately.