MAKE THE CRUST: Preheat the oven to 350 degrees. In a medium bowl, mix the cookie crumbs with the butter, sugar, and salt until the crumbs are evenly moistened. Pour the mixture into a 9-inch glass pie dish and press evenly over the bottom and up the side of the dish to form a crust. Bake for 8 minutes, until the crust is fragrant. Remove from the oven and, using the bottom of a drinking glass, immediately press the crumbs again to compact the crust. Let cool completely.

MAKE THE FILLING: In a medium saucepan, heat the milk with 1/4 cup of the sugar until bubbles form around the edge. In a large bowl, whisk the egg yolks with 1/4 cup of the sugar, the cornstarch, and salt. Gradually whisk in the hot milk mixture. Pour the mixture into the saucepan and cook over moderate heat, whisking constantly, until very thick, about 3 minutes. Remove from the heat and whisk in the semisweet and unsweetened chocolate until smooth. Strain the chocolate filling into the pie crust through a coarse sieve and smooth the surface with a rubber spatula. Press a piece of plastic wrap directly on the surface of the pie filling and refrigerate for 3 hours, until chilled.

Let the pie stand at room temperature for 10 minutes. Meanwhile, in a medium bowl, beat the cream with the remaining 2 tablespoons of sugar, and the vanilla until firm. Spread the whipped cream over the pie, cut into wedges and serve, garnished with chocolate shavings.

The pie can be made up to 1 day in advance and refrigerated.