Chocolate Peanut Butter Squares

• Preheat the oven to 375°F and set an oven rack in the middle position. Line a 9-inch square baking pan with heavy-duty aluminum foil so that there is a 2-inch overhang on all sides. Spray the foil with non-stick cooking spray.

Make the Crust

• Combine the Oreos (with their filling), butter, and peanut butter in the bowl of a food processor fitted with the blade attachment and pulse until the cookies are finely crushed. Press the mixture firmly into the prepared baking pan (I spread it with my hands first, then use the bottom of a measuring cup to even it out). Bake for 6 minutes. Set on a rack to cool completely.
• In the meantime, make the peanut butter filling: Combine all of the filling ingredients together in the bowl of a mixer fitted with the paddle attachment and mix at medium-low speed until evenly combined (do not whip). Set the bowl in the refrigerator while you prepare the rest.

Make the Chocolate Ganache

• Combine the chocolate chips and heavy cream in a microwave-safe bowl. Microwave on medium power (50%) for 1 minute, then stir until the bowl no longer feels warm. Continue heating in 15-second intervals, stirring each time until the chocolate is smooth and melted. The mixture may appear a bit gloppy and separated during the melting process — this is normal. However, it should become smooth and glossy once fully melted. Be careful not to overheat, as this can cause the chocolate to separate.

Assemble the Bars

• Drizzle ⅓ cup of the ganache evenly over the cooled crust; spread into a thin layer with an offset spatula—don't worry about making it perfect, and try not to crumble the crust. Place the pan in the freezer until the chocolate is set, about 10 minutes. Dollop the peanut butter filling over the chocolate, then use your hands to press it into an even layer. (If the mixture is sticky, dust your hands with confectioners' sugar.) Reheat the remaining chocolate mixture on full power for 15 to 20 seconds in the microwave and stir until smooth. Pour it over the peanut butter layer and use the offset spatula to smooth it to the edges. Place the bars in the freezer for 1 hour or in the refrigerator for 2 to 3 hours to set. Once firm, use the foil overhang to lift the bars onto a cutting board. Using a sharp chef's knife, cut into small squares, as they are very rich. Store the bars in the refrigerator and serve cold. They will keep nicely in the fridge for up to 4 days.