01 - Preheat the oven to 325°F (160°C). Grease a 9-inch springform pan and set aside.
02 - Pulse 24 Oreo cookies in a food processor until fine crumbs form. Drizzle in the melted butter and pulse until the mixture resembles wet sand. Press the crumb 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 with an electric mixer until smooth and creamy, about 2–3 minutes. Add the unsweetened cocoa powder and mix until fully incorporated. Blend in the melted and cooled semisweet chocolate chips until uniform.
04 - Add the eggs one at a time, beating well after each addition and scraping down the sides of the bowl as needed. Stir in the pure vanilla extract and sour cream until the batter is silky and fully combined.
05 - Gently fold the coarsely chopped Oreo cookies into the batter using a rubber spatula, being careful 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 any trapped air bubbles. Bake for 45 minutes, or until the center is just barely set with a slight jiggle remaining.
07 - Turn off the oven, crack the door open, and allow the cheesecake to rest inside for 1 hour. This gradual cooling helps prevent cracking.
08 - Remove the cheesecake from the oven. Run a thin knife around the edge to loosen it from the pan. Allow 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 — do not boil. Pour the hot cream over the semisweet chocolate chips in a heatproof bowl. Let sit for 1 minute, then stir gently until the ganache is smooth, glossy, and lump-free.
10 - Spread the chocolate ganache evenly over the chilled cheesecake. Arrange Oreo halves or crushed Oreo pieces on top for garnish. Refrigerate for at least 30 minutes before slicing and serving.