Prepare the Crust: 

1. In a medium bowl, combine the crushed Oreo cookies and melted butter. Mix until the crumbs are evenly coated with butter.
2. Press the mixture into the bottom and up the sides of a 9x2 inch pie dish. Use the back of a spoon or a flat-bottomed glass to compact the crust.
3. Place the crust in the refrigerator to set while you prepare the filling. 

Make the Chocolate Filling: 

1. In a heatproof bowl, combine the chopped dark chocolate and 1 cup of heavy whipping cream. Set the bowl over a pot of simmering water (double boiler method) and stir occasionally until the chocolate is fully melted and smooth.
2. Remove the bowl from the heat and let the chocolate mixture cool in the refrigerator for about 15 minutes.
3. In a separate large bowl, whip the cold heavy whipping cream (1 1/2 cups), powdered sugar, vanilla extract, and a pinch of kosher salt until stiff peaks form, about 4 minutes. Start on low before increasing speed.
4. Once the chocolate mixture has cooled (it can still be a little warm), gently fold in approximately ¾ of your homemade whipped cream until fully combined. Save the rest in the refrigerator for the topping. 

Assemble the Pie: 

1. Pour the chocolate filling into the prepared Oreo crust, spreading it evenly.
2. Cover the pie with plastic wrap and refrigerate for at least 6 hours, or until the filling is set and firm. 

Top with Whipped Cream: 

1. Before serving, take the remaining homemade whipped cream and spread or pipe it over the top of the pie.
2. Optionally, garnish with chocolate shavings or curls, and serve with sharp knife.