01 - Preheat oven to 325°F. Grease a 9-inch springform pan and line the bottom with parchment paper.
02 - Combine crushed chocolate sandwich cookies with melted butter until evenly moistened. Press the mixture firmly into the bottom of the prepared pan. Bake for 10 minutes, then set aside to cool.
03 - In a large mixing bowl, beat softened cream cheese and granulated sugar until completely smooth and free of lumps. Add smooth peanut butter and blend until fully incorporated.
04 - Add eggs one at a time, beating on low speed after each addition just until combined. Mix in vanilla extract and sour cream, being careful not to overbeat.
05 - Divide the filling mixture evenly into two portions. Fold the melted dark chocolate into one half, stirring until uniform in color.
06 - Pour the chocolate batter over the cooled crust and spread into an even layer. Spoon the peanut butter batter on top in dollops. Run a knife through the layers in gentle figure-eight motions to create a marbled effect.
07 - Bake for 50 to 60 minutes, until the edges are set and the center retains a slight jiggle when gently shaken.
08 - Turn off the oven and crack the door open. Allow the cheesecake to rest inside the cooling oven for 1 hour to prevent cracking.
09 - Transfer the cheesecake to the refrigerator and chill for at least 4 hours or overnight for best results.
10 - Heat heavy cream in a small saucepan until steaming. Remove from heat and add chopped dark chocolate, stirring until glossy and smooth. Stir in creamy peanut butter until blended. Cool slightly, then spread evenly over the chilled cheesecake.
11 - Scatter chopped roasted peanuts over the top if desired. Slice with a warm, clean knife and serve chilled.