01 - Preheat the oven to 325°F. Grease a 9-inch springform pan with butter or nonstick cooking spray.
02 - Pulse 24 Oreo cookies in a food processor until fine crumbs form. Add melted butter and pulse until evenly combined. Press the crumb mixture firmly and evenly into the bottom of the prepared springform pan. Bake for 10 minutes, then remove and set aside to cool.
03 - In a large mixing bowl, beat the softened cream cheese and granulated sugar with an electric mixer until completely smooth and creamy, about 2 to 3 minutes. Add the cocoa powder and blend until fully incorporated. Pour in the melted and cooled chocolate chips, mixing until the batter is uniformly chocolate-colored.
04 - Add the eggs one at a time, beating well after each addition to ensure even emulsification. Stir in the vanilla extract and sour cream, mixing just until combined. Avoid overmixing to prevent excess air in the batter.
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, smoothing the top with a spatula. Tap the pan firmly on the countertop several times to release trapped air bubbles. Bake for 45 minutes, or until the edges are set but the center still has a slight jiggle. Turn off the oven, crack the door open, and let the cheesecake rest inside for 1 hour.
07 - Remove the cheesecake from the oven. Run a thin knife around the edge of the pan to loosen the sides. Allow it to cool completely to room temperature, then transfer to the refrigerator and chill for at least 4 hours or preferably overnight.
08 - Heat the heavy cream in a small saucepan over medium heat until it just begins to simmer. Do not boil. Pour the hot cream over the chocolate chips in a heatproof bowl and let sit for 1 minute. Stir gently until the ganache is smooth, glossy, and free of lumps.
09 - Spread the chocolate ganache evenly over the chilled cheesecake. Arrange Oreo halves or sprinkle crushed Oreos on top for garnish. Refrigerate for at least 30 minutes before slicing and serving.