01 - Preheat the oven to 325°F (160°C). Grease a 9-inch (23 cm) springform pan.
02 - In a food processor, pulse 24 Oreo cookies into fine crumbs. Mix with melted butter until fully combined. Press the mixture firmly into the bottom of the springform pan. Bake for 10 minutes, then let cool.
03 - In a large bowl, beat the cream cheese and sugar until smooth and creamy. Add cocoa powder and mix well. Blend in the melted chocolate chips.
04 - Add eggs one at a time, mixing well after each addition. Stir in vanilla and sour cream until fully combined.
05 - Gently fold in the chopped Oreo cookies.
06 - Pour the filling over the cooled crust. Tap the pan to release air bubbles. Bake for 45 minutes or until the center is just set. Turn off the oven, crack the door, and let cheesecake cool for 1 hour inside.
07 - Remove from oven, run a thin knife around the edge, and allow to cool to room temperature. Refrigerate at least 4 hours or overnight.
08 - Heat heavy cream in a small saucepan until just simmering. Pour over chocolate chips and let sit for 1 minute, then stir until smooth and glossy.
09 - Spread the chocolate ganache over chilled cheesecake. Decorate with Oreo halves or crushed Oreos. Chill for at least 30 minutes before serving.