01 - Preheat the oven to 325°F. Grease a 9-inch springform pan and set aside.
02 - In a food processor, pulse 24 Oreo cookies into fine crumbs. Add the melted butter and pulse until evenly combined. Press the crumb mixture firmly into the bottom of the prepared springform pan to form an even layer. Bake for 10 minutes, then remove and let cool completely.
03 - In a large mixing bowl, beat the softened cream cheese and granulated sugar with an electric mixer until smooth and creamy. Add the cocoa powder and mix until fully incorporated. Blend in the melted and cooled chocolate chips until uniform.
04 - Add the eggs one at a time, mixing thoroughly after each addition. Stir in the vanilla extract and sour cream until the batter is completely smooth.
05 - Gently fold the coarsely chopped Oreo cookies into the batter using a rubber spatula, distributing them evenly throughout.
06 - Pour the filling over the cooled crust. Gently tap the springform pan on the counter several times to release any trapped air bubbles. Bake for 45 minutes, or until the center is just barely set with a slight jiggle.
07 - Turn off the oven, crack the door open, and allow the cheesecake to cool gradually inside the oven for 1 hour. This prevents cracking on the surface.
08 - Remove the cheesecake from the oven. Run a thin knife around the edge to loosen it from the pan. Allow it to cool to room temperature, then refrigerate for at least 4 hours or preferably overnight.
09 - Heat the heavy cream in a small saucepan over medium heat until it just begins to simmer. Pour the hot cream over the chocolate chips in a heatproof bowl. Let sit for 1 minute, then stir until the mixture becomes smooth, glossy, and fully combined.
10 - Spread the chocolate ganache evenly over the chilled cheesecake. Decorate with Oreo halves or crushed Oreo pieces. Refrigerate for at least 30 minutes before slicing and serving.