Preheat your oven to 350°F (175°C). Line a 9x13-inch baking pan with foil, leaving an overhang for easy removal, and lightly spray with non-stick cooking spray. Combine crushed Oreo cookies with melted butter, then press into the pan. Bake for 10 minutes.

Lower oven temperature to 325°F (160°C). Melt bittersweet chocolate over simmering water until smooth; set aside. Blend softened cream cheese until creamy, then add granulated and light brown sugar. Incorporate cocoa powder, eggs, heavy cream, and vanilla until just combined. Fold in melted chocolate.

Pour the filling over the pre-baked crust and spread evenly. Bake for approximately 35 minutes until edges are set and center is slightly jiggly. Cool on a wire rack for about 30 minutes, then refrigerate for at least 4 hours or overnight.

Heat heavy cream until simmering. Pour hot cream over chopped semi-sweet chocolate. Let sit, then whisk until smooth. Allow to cool slightly before pouring over the chilled bars.

Once ganache has set, lift bars out of the pan using the foil overhang. Slice into squares using a thin-bladed knife, wiping the knife clean between cuts.