For Chocolate Cookie Crust

1. Preheat the oven to 350°F. Line an 8 x 8 inch baking pan with parchment paper. Allow the paper to hang over the sides of the pan by a couple of inches for easy removal of the bars once baked. Set aside.
2. Pulse about 20 Oreo cookies (with the filling removed) in the bowl of a food processor until finely ground. You should have about 2 cups of cookie crumbs.
3. Transfer the crumbs to a medium bowl and add the melted butter. Stir with a fork until all of the crumbs are coated in the butter.
4. Transfer the cookie crumbs to the prepared pan and use your hands or the bottom of a measuring cup to press the crumbs evenly into the corners of the pan. 
5. Bake for 10 minutes. Remove from the oven and set aside to cool while you make the filling.

For Chocolate Cream Filling

1. Use a double boiler to melt the butter and chocolate over medium-low heat. To create a double boiler, place a heat safe bowl over a medium pot filled with 2 inches of water. Bring the water to a simmer and stir frequently as the chocolate and butter melt. Stir until melted and smooth. Remove the bowl from the pot, being careful not to let any of the condensation from the water drip into the chocolate mixture. Set aside to cool for 10 minutes.
2. While the chocolate is cooling, whip together 1 cup of heavy whipping cream with 2 tablespoons of powdered sugar until firm peaks form. Place the bowl in the refrigerator to keep cold. 
3. In a large bowl, add the softened cream cheese, powdered sugar, cocoa powder, vanilla and salt. Use a hand mixer to mix until smooth, about 1 minute. 
4. Add the cooled chocolate mixture to the bowl and mix on low speed for about 30 seconds until well combined.
5. Remove the whipping cream from the refrigerator and use a large spatula to fold half of the cream into the chocolate mixture. Before it is fully combined, add the remaining whipped cream and gently fold together until no white streaks remain.
6. Transfer the filling to the top of the cookie crust and use an offset spatula to press it into the corners of the pan and level the top.
7. Chill for 3 hours or overnight.
8. Before serving, whip 1 cup of heavy whipping cream together with 2 tablespoons of powdered sugar and vanilla. Whip until smooth and firm. 
9. Transfer the whipped cream to the top of the filling and use an offset spatula or spoon to spread it evenly across the top. Top with chocolate shavings or curls if desired.
10. For best results, chill the bars for 30 minutes before using a sharp knife to cut into squares. Clean the knife between each slice with hot water and wipe with a dry dishtowel.