Preheat your oven to 375°F (190°C) and set an oven rack in the middle position.
Line a 9-inch square baking pan with heavy-duty aluminum foil, allowing a 2-inch overhang on all sides.
Spray the foil with non-stick cooking spray.
In a food processor, combine the Oreo cookies (filling included), butter, and peanut butter. Pulse until the cookies are finely crushed and the mixture is combined.
Press the Oreo mixture firmly into the prepared baking pan.
Bake the crust for about 6 minutes until it sets slightly.
While the crust cools, prepare the peanut butter filling by combining the dark brown sugar, Confectioners' sugar, unsalted butter, and creamy peanut butter.
In a microwave-safe bowl, combine the milk chocolate chips and heavy cream.
Microwave on medium power (50%) for 1 minute, stirring until smooth.
Drizzle the ganache evenly over the cooled crust.
Place the pan in the freezer for about 10 minutes to let the chocolate set.
Dollop the chilled peanut butter filling over the chocolate layer and press it evenly.
Reheat the remaining chocolate mixture and pour it over the peanut butter layer.
Place the bars in the freezer for 1 hour or refrigerate for 2 to 3 hours to set.
Once firm, cut the bars into squares and serve cold.