Make the crust. In a small bowl, combine the gingersnap crumbs, butter, and granulated sugar. Press the crumb mixture into a 9-inch pie pan and bake for 6 minutes. Remove the pan from the oven and cool on a wire rack.
Make the filling. In a small bowl, combine the gelatin with 1/2 cup cool water and let sit for 5 minutes until the gelatin softens and blooms.
In a medium saucepan set over medium-high heat, bring the milk, cocoa, 1/4 cup of the granulated sugar, and the salt just to a simmer, stirring constantly. Remove the pan from the heat and add the gelatin, stirring until the gelatin is completely dissolved.
Put the egg yolks into a medium bowl and beat lightly. Gradually, in a slow stream, add 1/2 cup of the chocolate mixture to the egg yolks while whisking continually. Pour the chocolate-egg yolk mixture into the pan with the remaining chocolate mixture. Cook, stirring constantly, over medium heat until slightly thickened, about 8 minutes. Remove the pan from the heat and let cool for about 20 minutes or until barely warm.
Using an electric mixer, in a large bowl, whip the egg whites to soft peaks. Add the remaining 2 tablespoons granulated sugar and the vanilla, and whip to stiff peaks. Gently fold the cooled chocolate mixture into the meringue in three additions.
Spoon the chocolate mixture into the cool pie crust. Cover and refrigerate for 2 hours.
Whip the cream with the confectioners' sugar. Place dollops of cream over the pie. Grate the semisweet chocolate over the pie.