01 - Preheat oven to 325°F. Grease a 9-inch springform pan and line the bottom with parchment paper.
02 - Combine the crushed chocolate sandwich cookies with the melted butter until the mixture resembles wet sand. Press firmly and evenly into the bottom of the prepared pan. Bake for 10 minutes, then set aside to cool completely.
03 - In a large mixing bowl, beat the softened cream cheese and granulated sugar together using a hand or stand mixer until completely smooth and free of lumps. Blend in the smooth peanut butter until fully incorporated.
04 - Add the eggs one at a time, beating on low speed after each addition just until combined. Stir in the vanilla extract and sour cream, being careful not to overmix.
05 - Divide the filling mixture evenly into two bowls. Fold the melted dark chocolate into one half, stirring gently until uniform in color. Leave the other half as the plain peanut butter mixture.
06 - Pour the chocolate filling over the cooled crust and spread into an even layer. Spoon dollops of the peanut butter filling on top, then run a butter knife or skewer through both layers in gentle figure-eight motions to create a marbled effect.
07 - Bake on the center rack for 50 to 60 minutes. The edges should be set and lightly golden while the center retains a subtle jiggle when gently shaken.
08 - Turn off the oven, crack the door open slightly, and allow the cheesecake to rest inside for 1 hour. This gradual cooling helps prevent cracking on the surface.
09 - Transfer the cheesecake to the refrigerator and chill for at least 4 hours, or preferably overnight, until fully set and firm.
10 - Heat the heavy cream in a small saucepan until steaming but not boiling. Remove from heat, add the chopped dark chocolate, and stir until the ganache is silky smooth. Blend in the creamy peanut butter. Allow the topping to cool slightly, then spread it evenly over the chilled cheesecake.
11 - Sprinkle chopped roasted peanuts over the topping if desired. Slice with a sharp knife dipped in hot water for clean portions. Serve chilled.