Preheat & Prep: Preheat your oven according to the brownie mix instructions. Line a 9x13-inch pan with aluminum foil or parchment paper and lightly spray with cooking oil.
Brownie Base: Prepare the brownie batter as per the box instructions, but reduce the amount of oil by 20%. Pour into the prepared pan and bake. Once done, allow the brownies to cool completely.
Marshmallow Magic: Gently spread the jar of marshmallow cream evenly over the cooled brownies.
Chocolate-Peanut Butter Bliss: In a microwave-safe bowl, combine the chocolate chips and peanut butter. Melt in the microwave in one-minute increments, stirring after each minute until smooth.
Crunch Time: Mix in the Rice Krispies into the melted chocolate-peanut butter mixture until well incorporated.
Final Assembly: Evenly spread the chocolate-peanut butter crunch layer over the marshmallow layer. Use a spatula to smooth out the surface.
Chill: Place the assembled dessert in the refrigerator for at least 2 hours to set.
Slice & Serve: After chilling, remove from the fridge and cut into bars. Serve chilled or at room temperature.