Preheat the oven to 400 degrees F.

In a food processor, combine the vanilla wafers, 1/4 cup sugar, and pecan pieces. Mix until the crust is smooth and resembles a coarse texture. With the machine running, add the butter and process until all of the butter is incorporated. Remove the crust from the processor and press into a deep-dish 10-inch pie pan. Place the pan in the oven and bake for 10 to 12 minutes or until the crust is set.

In a saucepan, combine the eggnog, sweet potatoes, brown sugar, egg yolks, cinnamon, nutmeg, salt, and ginger together. Mix well. Place the pan over medium heat and cook the mixture for 10 minutes, stirring constantly.

Remove the pan from the heat and sprinkle the gelatin over the filling. Whisk the gelatin into the filling until the gelatin dissolves. Stir in the vanilla. Cover the filling and refrigerate until cool.

Using an electric mixer, whip the egg whites until soft peaks form. Gradually add 1/4 cup sugar and continue to beat until the peaks are stiff. Fold the egg whites into the sweet potato filling. Spread the filling evenly over the crust and refrigerate the pie for about 1 hour.

Spread the whipped cream, evenly over the top of the pie.

Slice the pie into 8 pieces. Place a piece of the pie on each serving plate. Garnish with confectioners' sugar and a sprig of fresh mint.