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 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.
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. Avoid overmixing to prevent excess air in the batter.
05 - Divide the filling mixture evenly into two bowls. Fold the melted dark chocolate into one half, mixing 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. Gently spoon the peanut butter filling on top. Run a knife or offset spatula through the layers in sweeping motions to create a marbled effect.
07 - Bake on the center rack for 50 to 60 minutes, until the edges are firmly set and the center still has a slight jiggle when gently shaken.
08 - Turn off the oven, crack the door open slightly, and let the cheesecake rest inside for 1 hour. This gradual cooling helps prevent surface cracks.
09 - Transfer the cheesecake to the refrigerator and chill for at least 4 hours, or preferably overnight, until completely set.
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 smooth and glossy. Stir in the creamy peanut butter until well blended. Let the ganache cool slightly until it thickens to a spreadable consistency.
11 - Spread the ganache topping evenly over the chilled cheesecake. Garnish with chopped roasted peanuts if desired. Slice with a sharp knife dipped in hot water for clean portions, then serve.