Preheat your oven to 325°F (160°C) to ensure even cooking of the cheesecake bars.
In a mixing bowl, combine the crushed Oreo cookies with melted butter. Stir until well coated and press firmly into the bottom of a greased 9x13-inch baking pan using the back of a measuring cup.
Bake the crust in the preheated oven for about 10 minutes. Remove and let cool slightly while preparing the filling.
Melt the bittersweet chocolate in a double boiler or microwave-safe bowl until smooth, stirring every 30 seconds if microwaving. Set aside to cool slightly.
Using an electric mixer, beat room-temperature cream cheese until smooth and creamy. Gradually add granulated and brown sugars, mixing well. Add cocoa powder, eggs, and egg yolks, beating until just combined.
Slowly pour melted chocolate and 1 cup heavy cream into the cream cheese mixture. Add vanilla extract and mix until fully combined and smooth.
Pour the cheesecake filling over the cooled Oreo crust and spread evenly with a rubber spatula.
Bake cheesecake for 50-60 minutes until the center is set but slightly jiggly. Turn off oven and leave door ajar, letting cheesecake cool gradually for about an hour.
Refrigerate the cheesecake for at least 4 hours or overnight to fully set.