Preheat your oven to 325°F (160°C). Prepare a 9X9-inch square pan with nonstick spray and line with parchment paper.

Pulse the Oreo cookies into fine crumbs and mix with melted butter. Press into the prepared pan to form the crust and bake for 12 minutes.

Melt the chocolate bar in a microwave-safe bowl in 30-second intervals until smooth.

In a stand mixer, combine cream cheese, sugar, and cocoa powder. Beat until creamy, then mix in melted chocolate, heavy cream, and vanilla until smooth.

Fold in eggs one at a time, mixing just until combined without overmixing.

Pour the cheesecake batter over the baked crust and smooth the top. Bake for 40-50 minutes until edges are set, and the center jiggles slightly.

Cool in the oven with the door slightly open for 20 minutes. Then transfer to a cooling rack to cool completely, then chill in the refrigerator for at least 6 hours.

For the ganache, simmer heavy cream and pour over chocolate chips. Let sit before stirring until smooth.

Remove the cheesecake from the pan and pour ganache over the top. Freeze for 10 minutes before slicing into bars.