Preheat your oven to 325°F (165°C). Line a 9x13-inch baking pan with parchment paper, leaving some overhang on the sides. This will make it easy to lift the bars out after baking.

Place the chocolate sandwich cookies into a food processor and pulse until fine crumbs form. Alternatively, place them in a sealed bag and crush with a rolling pin. Transfer crumbs to a bowl and mix with melted butter until evenly moistened.

Press the mixture firmly into the bottom of the prepared pan, creating an even layer. Use the bottom of a measuring cup to compact the crust. Bake for 10 minutes, then remove from the oven and allow to cool slightly.

In a large mixing bowl, beat the softened cream cheese until smooth and creamy, about 2–3 minutes. Add the granulated sugar and continue beating until fully incorporated.

Sift in the cocoa powder and mix until combined. Add the melted chocolate and beat gently until smooth. Scrape down the sides of the bowl as needed.

Add the eggs one at a time, mixing on low speed after each addition. Avoid overmixing. Stir in the sour cream, vanilla extract, and salt until just combined.

Pour the cheesecake filling over the cooled crust. Use an offset spatula to smooth the top evenly.

Bake in the preheated oven for 40–45 minutes, or until the edges are set and the center is slightly jiggly. Do not overbake, as the cheesecake will continue to firm up as it cools.

Turn off the oven, crack the door slightly, and allow the bars to cool inside for 30 minutes. This gradual cooling helps prevent cracks.

Remove the pan from the oven and let it cool completely at room temperature. Once cooled, refrigerate for at least 4 hours, preferably overnight, to allow the cheesecake to fully set.

Heat heavy cream until just steaming, then pour over chopped chocolate. Let sit for 2 minutes, then stir until smooth. Spread evenly over the chilled cheesecake and refrigerate until set.