01 - Preheat the oven to 325°F. Grease a 9-inch springform pan and line the bottom with parchment paper. Wrap the outside of the pan tightly with aluminum foil if using a water bath.
02 - Combine the crushed chocolate sandwich cookies with the melted butter in a bowl until the mixture resembles wet sand. Press the crumb mixture 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 on medium speed until completely smooth and free of lumps. Add the smooth peanut butter and blend 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, mixing gently to avoid incorporating excess air.
05 - Divide the filling mixture evenly into two separate bowls. Fold the melted dark chocolate into one half, stirring until the color is uniform. Leave the other half as the plain peanut butter mixture.
06 - Pour the chocolate batter over the cooled crust and spread into an even layer. Gently spoon the peanut butter batter on top in dollops. Run a butter knife or offset spatula through the layers in sweeping curves to create a marbled effect.
07 - Place the cheesecake on the center rack and bake for 50 to 60 minutes. The edges should be set and lightly golden while the center retains 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 cracks from forming on the surface.
09 - Transfer the cheesecake to the refrigerator and chill for at least 4 hours or preferably overnight to allow the filling to set completely.
10 - Heat the heavy cream in a small saucepan until steaming but not boiling. Remove from heat, add the chopped dark chocolate, and let sit for 2 minutes. Stir until smooth and glossy, then blend in the creamy peanut butter. Let the ganache cool slightly until it reaches a spreadable consistency.
11 - Spread the ganache topping evenly over the chilled cheesecake. Garnish with chopped roasted peanuts if desired. Slice with a warm, clean knife and serve.