Instructions

• Preheat the oven to 375°F and place a rack in the middle position. Line a 9-inch square baking pan with heavy‑duty aluminum foil so there is a 2‑inch overhang on all sides; spray the foil with nonstick cooking spray.
• Make the crust: Place 22 Oreo cookies (with their filling), 3 tablespoons softened butter, and 2 tablespoons creamy peanut butter in the bowl of a food processor fitted with the blade. Pulse until the cookies are finely crushed and the mixture is uniform.
• Press the cookie mixture firmly and evenly into the prepared pan (spread with your hands, then tamp and smooth with the bottom of a measuring cup). Bake the crust for 6 minutes. Remove from the oven and set the pan on a wire rack to cool completely.
• While the crust cools, make the peanut butter filling: In the bowl of a stand mixer fitted with the paddle attachment combine 1/3 cup (packed) dark brown sugar, 2 cups confectioners' sugar, 6 tablespoons unsalted butter (softened), 1 1/3 cups creamy peanut butter, and 1/8 teaspoon salt. Mix on medium‑low speed just until evenly combined (do not whip). Transfer the bowl to the refrigerator to chill while you prepare the chocolate.
• Make the chocolate ganache: Put the entire 11.5‑ounce bag of milk chocolate chips and 6 tablespoons heavy cream in a microwave‑safe bowl. Microwave at 50% power for 1 minute, then stir. Continue microwaving in 15‑second intervals at 50% power, stirring after each interval, until the chocolate is smooth and fully melted. (It may look slightly separated during melting but should finish smooth. Avoid overheating.)
• Measure out 1/3 cup of the melted chocolate mixture and drizzle it evenly over the cooled crust. Use an offset spatula to spread it into a thin layer (don’t press into the crust). Put the pan in the freezer until this chocolate layer is set, about 10 minutes.
• Remove the peanut butter filling from the refrigerator. Dollop the filling over the set chocolate in even spoonfuls. Use your hands to press the dollops into an even layer across the pan; if the filling is sticky, dust your hands lightly with confectioners' sugar.
• Reheat the remaining chocolate ganache: microwave it on full power for 15–20 seconds, then stir until smooth. Pour the warmed ganache over the peanut butter layer and smooth it to the edges with an offset spatula.
• Chill the assembled bars until firm: place in the freezer for 1 hour or in the refrigerator for 2–3 hours.
• Use the foil overhang to lift the set slab from the pan onto a cutting board. Using a sharp chef’s knife, cut into small squares. Store the bars in the refrigerator and serve cold; they will keep up to 4 days.