01 - Preheat oven to 325°F. Grease a 9-inch springform pan with butter or nonstick spray and set aside.
02 - Pulse 24 Oreo cookies in a food processor until fine crumbs form. Pour in melted butter and process until the mixture resembles wet sand. Press 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 softened cream cheese and granulated sugar with an electric mixer on medium speed until smooth and creamy, about 2 to 3 minutes. Add cocoa powder and blend until fully incorporated. Pour in the melted and cooled chocolate chips, mixing until homogeneous.
04 - Add eggs one at a time, beating well after each addition and scraping down the sides of the bowl. Stir in vanilla extract and sour cream until the batter is silky and uniformly combined.
05 - Gently fold the coarsely chopped Oreo cookies into the batter using a rubber spatula, taking care not to overmix.
06 - Pour the filling over the cooled crust, smoothing the top with a spatula. Tap the pan firmly on the counter several times to release trapped air bubbles. Bake on the center rack for 45 minutes, or until the edges are set and the center has a slight jiggle.
07 - Turn off the oven and crack the door open. Let the cheesecake rest inside the warm oven for 1 hour to prevent cracking. Remove from the oven, run a thin knife around the edge of the pan, and allow it to cool to room temperature. Refrigerate for at least 4 hours or preferably overnight.
08 - Heat 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. Let sit undisturbed for 1 minute, then stir slowly from the center outward until the ganache is smooth, glossy, and lump-free.
09 - Spread the ganache evenly over the chilled cheesecake. Arrange Oreo halves or sprinkle crushed Oreos on top for garnish. Return to the refrigerator and chill for at least 30 minutes before slicing and serving.