1. Preheat oven to 325°F (160°C). Grease a 9-inch springform pan and line the bottom with parchment paper.

2. Mix chocolate cookie crumbs, sugar, and melted butter until combined. Press firmly into the bottom of the pan. Bake for 10 minutes, then cool slightly.

3. In a large bowl, beat cream cheese and sugar until smooth and creamy.

4. Add cocoa powder and mix well.

5. Beat in eggs one at a time, then add sour cream, melted chocolate, orange zest, orange juice, and vanilla. Mix until smooth.

6. Pour filling over the crust and smooth the top.

7. Bake for 55–65 minutes or until the center is just set but still slightly jiggly.

8. Turn off the oven, crack the door open, and let the cheesecake cool inside for 1 hour.

9. Remove and cool completely, then refrigerate for at least 4 hours or overnight.

10. For the ganache, heat heavy cream until just simmering. Pour over chopped chocolate and stir until smooth. Stir in orange zest.

11. Pour ganache over chilled cheesecake and spread evenly. Chill for 30 minutes to set.

12. Top with candied orange slices or chocolate curls before serving.