Preheat the oven to 400ºF.

Combine the ground vanilla wafers and chopped pecans in a blender or food processor. Pulse once or twice to blend. With the machine running, add the butter and process until blended. Press the mixture into the bottom and up the sides of a 9-inch deep-dish pie pan and bake until golden and fragrant, 10 to 12 minutes.

In a large saucepan, combine the eggnog, pumpkin, brown sugar, egg yolks, cinnamon, nutmeg, salt, and ginger and mix well. Place over medium heat and cook, stirring constantly, until mixture thickens slightly and boils around the edges. While the mixture is cooking, sprinkle the gelatin over the bourbon in a small bowl and set gelatin aside to bloom.

When the pumpkin mixture has thickened slightly and is bubbly, remove from the heat and stir in the gelatin mixture. Whisk until the gelatin dissolves, then stir in the vanilla extract. Cover and refrigerate for 1 hour, stirring occasionally, until cooled.

Beat the egg whites with an electric mixer in a medium-size mixing bowl until soft peaks form. Gradually add the granulated sugar and continue to beat until the peaks are stiff. Fold the egg whites into the pumpkin mixture. Spread evenly over the crust and refrigerate until the filling is completely set, at least 2 hours and up to overnight.

Spread the whipped cream evenly over the top of the pie, garnish with the pecan halves, and serve.