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 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. Add the 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. Mix in the vanilla extract and sour cream, being careful not to overbeat.
05 - Divide the filling mixture evenly into two separate bowls. Fold the melted dark chocolate into one half and stir until uniformly blended. 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 butter knife or offset spatula through the batter in sweeping curves to create a marbled pattern.
07 - Bake for 50 to 60 minutes, until the edges are set and the center still has a slight jiggle when gently shaken. Avoid overbaking, as the residual heat will continue to set the center.
08 - Turn off the oven, crack the door open slightly, and allow the cheesecake to cool 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 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 smooth and glossy. Stir in the peanut butter until well blended. Let the mixture 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.