Oreo Crust

1. Line a square pan ( 8×8-inch or 9×9 inch) with parchment paper aluminum foil and  set aside.
2. In a medium bowl, mix the Oreo cookie crumbs and melted butter together. Using the back of a large spoon or cup, press mixture evenly into the bottom of the prepared pan. Place in the freezer to set while preparing the cheesecake filling.

Chocolate Cheesecake Filling

1. In a large bowl, beat the heavy whipping cream and ¼ cup of the powdered sugar until stiff peaks form.
2. In a separate medium-size bowl, beat together the cream cheese and remaining powdered sugar until soft. Mix in the sour cream, cooled melted chocolate, and vanilla extract.
3. Carefully fold the whipped cream into the cream cheese mixture until well combined. Spread evenly over the top of the prepared  Oreo crust.
4. Place the cheesecake bars covered in the fridge for at least 4 hours to set. Cut into slices. Serve with fresh whipped cream and berries. You could also drizzle with chocolate sauce, if desired.