Preheat oven to 350°F. Using your food processor, pulse together the cookies and melted butter until it resembles wet sand. Press the crumb mixture on the bottom and up the sides of a 9-inch pie plate. Bake until crisp, for about 10-15 minutes, and cool on a rack.

Over medium heat, whisk together the sugar, cornstarch, salt, and yolks in a 3-quart heavy saucepan until well combined. Then slowly add in the milk, whisking. Bring to a boil over moderate heat, still whisking, then reduce heat and simmer, whisking some more for about 1 minute (filling will be thick).

If you're up for this: Force filling through a fine-mesh sieve into a bowl, then whisk in chocolate, butter, and vanilla. Cover and allow to cool completely, for about 2 hours. Spoon filling into your baked crust and chill the pie, loosely covered, for at least 6 hours.

Using your stand mixer fitted with the whisk attachment, beat the cold heavy cream with the sugar until it just holds stiff peaks, after 3-4 minutes. Spread on top of the chocolate pie, sprinkle on chocolate shavings or chocolate sprinkles and serve.