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 in a medium bowl until the mixture resembles wet sand. Press the mixture firmly and evenly into the bottom of the prepared springform pan. Bake for 10 minutes, then remove and let 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 introducing excess air.
05 - Divide the filling mixture evenly into two separate bowls. Fold the melted dark chocolate into one half, stirring until uniformly blended. 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. Spoon the peanut butter batter on top in dollops. Run a butter knife or offset spatula through the layers in gentle swirling motions to create a marbled effect.
07 - Place the cheesecake in the center of the oven 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 and crack the oven door open. Allow the cheesecake to rest inside the cooling oven 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, preferably overnight, until completely set and firm.
10 - In a small saucepan, heat the heavy cream over medium-low heat until steaming but not boiling. Remove from heat, add the chopped dark chocolate, and stir until silky smooth. Stir in the creamy peanut butter until well blended. 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.