Prepare the crust: Preheat your oven to 350°F (175°C). In a mixing bowl, combine the chocolate cookie crumbs, melted butter, and granulated sugar. Stir until the mixture resembles wet sand. Press the mixture firmly into the bottom of a 9-inch springform pan. Bake for 8-10 minutes. Remove from the oven and let cool.
Make the cheesecake filling: In a large mixing bowl, beat the softened cream cheese with an electric mixer until smooth and creamy. Add in the creamy peanut butter and powdered sugar; mix until combined.
Incorporate flavors: Add the vanilla extract and mix until well combined. Slowly add the eggs, one at a time, mixing on low speed after each addition just until incorporated. Be careful not to overmix.
Add remaining ingredients: Fold in the sour cream and heavy cream gently with a spatula. Finally, pour in the melted dark chocolate and mix until the batter is smooth and uniform.
Bake the cheesecake: Pour the filling over the cooled crust, smoothing the top with a spatula. Bake in the preheated oven for 45-50 minutes, or until the edges are set but the center is still slightly jiggly. Turn off the oven and leave the cheesecake inside with the door slightly ajar for about 1 hour.
Cool and chill: Remove the cheesecake from the oven and allow it to cool to room temperature. Once cooled, refrigerate for at least 4 hours or overnight for best results.
Prepare the topping: Before serving, whip the heavy cream to soft peaks. Arrange the whipped cream on top of the cheesecake in an even layer. Drizzle the warmed peanut butter over the cream, and finish by garnishing with chocolate shavings or chips.