Line the base of a 9-inch springform pan with parchment. Chill a large mixing bowl and beaters in the fridge for 10 minutes so the cream whips efficiently.
Make the topping first: In the chilled bowl, whip 1 1/4 cups cold cream with 1/3 cup powdered sugar and 1/2 teaspoon vanilla on medium-high until medium-firm peaks form, 2–3 minutes. Transfer to a piping bag or cover the bowl; refrigerate until ready to finish the pie.
For the crust, pulse the chocolate sandwich cookies in a food processor until very fine. Add melted butter and pulse just until the crumbs are evenly moistened. Press the mixture firmly into the pan, going about 1 1/2 inches up the sides. Freeze 15 minutes to set while you prepare the filling.
Melt 5 ounces of chopped dark chocolate in a heatproof bowl set over a saucepan with barely simmering water, stirring until smooth. Remove from heat and let cool 5 minutes so it’s warm but not hot.
In a clean bowl, beat the cold 3/4 cup cream with the cocoa powder and 2 tablespoons powdered sugar on medium-high just to medium peaks (soft, gently curving tips). Set aside.
In a separate large bowl, beat the cream cheese until very smooth and fluffy, 1–2 minutes. Mix in the marshmallow creme until no streaks remain, then beat in 1 teaspoon vanilla and the espresso powder.
With the mixer on low, stream in the melted chocolate and blend just until combined, scraping the bowl as needed. Gently fold in the cocoa whipped cream in two additions, followed by the remaining 3 ounces finely chopped chocolate.
Scrape the filling into the chilled crust, smooth the top, and tap the pan firmly on the counter a few times to release air pockets. Chill until set, about 2 1/2 to 3 hours.
Right before serving, pipe or spoon the reserved whipped cream topping over the chilled pie. Garnish with crushed Oreos and chocolate curls.
Slice with a thin knife run under hot water and wiped dry between cuts for extra-clean slices. Serve cold.