For the crust: Preheat the oven to 350 degrees F. Place the cookies, pecans and salt in the bowl of a food processor. Pulse until they form fine crumbs. Add the melted butter and process until combined. Press into the bottom and up the sides of a 9-inch pie plate. Refrigerate until firm, about 10 minutes.
Meanwhile, for the filling: Place the butter and bittersweet chocolate in a microwave-safe bowl. Microwave for 2 minutes, stirring every 30 seconds until the mixture is melted. Stir until smooth.
In a large bowl, combine the sour cream and espresso powder. Whisk in the granulated sugar, light corn syrup, vanilla extract and eggs. Fold in the melted chocolate. Pour the filling into the prepared pie shell. Place the pie on a baking sheet and bake until the filling puffs and looks cracked around the edges, but is still slightly jiggly in the middle, about 35 minutes. Cool the pie completely. It will fall as it cools.
For the topping: After the pie is completely cool, beat the heavy cream, confectioners' sugar and vanilla until soft peaks form. Spread the cream onto the pie. Garnish with chopped pecans and chocolate shavings.
Cook's Note: To make nice large chocolate curls, start with room-temperature chocolate, and run a vegetable peeler along its side.