Grease a 9" x 13" baking dish with non-stick cooking spray.

For the Rice Krispies layer: In a large microwave-safe bowl, microwave 6 tablespoons of butter until melted.

Add the marshmallows to the bowl of melted butter and return to the microwave for 1 to 2 minutes or until marshmallows are melted, stirring in 30-second intervals.

Add Rice Krispies and pretzels. Stir to combine and immediately press into the prepared baking dish. Use wax paper to press down as the mixture will be very sticky. Place dish in the fridge while you prepare the next layer.

For the peanut butter layer: Combine the butter and corn syrup in a microwave-safe bowl. Heat in the microwave for 45-60 seconds or until the butter is melted, stirring halfway.

Add the peanut butter chips and stir well. Return to microwave and cook for another 30-40 seconds or until the chips are melted, stirring halfway. Spread the peanut butter mixture over the cereal layer. And place in the fridge while you prepare the chocolate layer.

For the chocolate layer: Place the butter and corn syrup in a microwave-safe bowl and heat for 45-60 seconds, or until the butter is melted, stirring halfway. Add the chocolate chips to the bowl and stir. Return to microwave and cook for a further 30-40 seconds, until the choc chips are melted, stirring halfway through. Spread the chocolate over the peanut butter layer.

For the Monster Crunch topping: While the chocolate is still warm, arrange the candy eyes over the top, along with all the other topping ingredients. Press down gently so that everything sticks to the chocolate.

Return to the fridge to set completely.

Cut into bars and serve.

Store in an airtight container for up to one week.