Instructions

• Line an 8×8-inch pan with parchment paper or aluminum foil, leaving an overhang on two sides for easy removal; set the pan aside.
• In a large mixing bowl, beat the softened unsalted butter and packed light brown sugar together on medium speed until light and fluffy, about 3 minutes.
• Add the vanilla extract and beat until incorporated, scraping down the bowl as needed.
• Reduce the mixer speed to low. Add the all-purpose flour and the sweetened condensed milk alternately in batches, mixing after each addition just until combined and no large streaks remain.
• Gently fold in the mini chocolate chips with a spatula until evenly distributed.
• Transfer the dough to the prepared pan. Press it evenly into the bottom of the pan (the dough will be sticky—lightly flour your hands or use a piece of parchment or an offset spatula to press it down).
• Cover the pan with plastic wrap and refrigerate until firm, about 3 hours or overnight.
• To make the topping, place the creamy peanut butter and the milk chocolate chips in a microwave-safe bowl. Microwave in 20–30 second intervals, stirring between intervals, until the mixture is smooth and pourable.
• Pour and evenly spread the peanut butter–chocolate mixture over the chilled cookie dough.
• Return the pan to the refrigerator and chill until the topping is set, at least 1 hour.
• Use the parchment or foil overhang to lift the block from the pan, place on a cutting board, and cut into bars.