Preheat oven to 325°F.  Line an 8-inch square baking pan with aluminum foil, making sure to leave some overhang for easy removal, and set aside.  Add the Oreos to the bowl of a food processor and process until you have fine crumbs.  Add in the melted butter and process until all of the crumbs are moistened.

Scoop the mixture into the prepared baking pan and press it down firmly in an even layer.  Bake at 325°F for 10 minutes.  Remove from the oven and set aside to cool.

In a large mixing bowl, using an electric mixer, beat the cream cheese until smooth.  Add in the granulated sugar, peanut butter, and vanilla extract and mix until fully combined.  Add in the egg and mix on low speed until well combined.  Set aside.

In a large mixing bowl, using an electric mixer, beat the cream cheese until smooth.  Add in the granulated sugar, melted chocolate, and vanilla extract and mix until fully combined.  Add in the egg and mix on low speed until well combined.  Set aside.

Pour the peanut butter cheesecake filling over the prepared crust.  Spread the mixture evenly over the crust, making sure to smooth the top out as well as possible.  Gently add the chocolate cheesecake filling on top of the peanut butter cheesecake filling and smooth the top out.  Bake at 325°F for about 35 minutes or until set.  Remove from the oven and cool completely in the pan on a wire rack (for about two hours).  Transfer to the refrigerator for about 3 hours or until the cheesecake is completely chilled.  Lift the cheesecake out of the pan with the foil and slice into bars.

Store in an airtight container in the refrigerator for up to four days.