Combine crushed chocolate sandwich cookies with melted butter, then press this mixture evenly into a 9-inch pie plate. Bake the crust at 350°F (175°C) for 8-10 minutes, then remove and cool completely.

In a mixing bowl, beat softened unsalted butter and granulated sugar together until the mixture becomes light and fluffy. Gradually incorporate the eggs one at a time, ensuring each is fully blended before adding the next.

Stir in the unsweetened cocoa powder, salt, and vanilla extract until well combined. Slowly pour in the heavy cream and continue to beat until the chocolate filling is smooth and uniform.

Pour the prepared chocolate filling into the cooled pie crust, spreading it evenly. Refrigerate the pie for a minimum of 4 hours, or until the filling is firm and set.

In a separate chilled bowl, whip the cold heavy cream with powdered sugar and vanilla extract until stiff peaks form.

Spread or pipe the whipped cream generously over the chilled pie just before serving. Garnish the pie with chocolate shavings or a dusting of cocoa powder as desired.