Prepare a 9” square pan with a lining of parchment paper, leaving an overhang on two opposite sides (see my photos in this post). Set aside.

In a large pot over medium to medium-low heat, melt the butter. Turn heat down to low and add 8 cups of the miniature marshmallows. Stir constantly until completely smooth and then remove pan from heat. Quickly stir in the peanut butter and salt until smooth. Then fold in the Rice Krispies cereal, half of the chopped Oreo cookies, and 1-1/2 cups of miniature marshmallows. The mixture will be very thick. Work quickly to incorporate everything evenly, and to avoid over mixing.

Transfer mixture to prepared pan and very gently create an even layer of Rice Krispies treats. I like to use the buttery side of the butter wrapper to gently press on the mixture, for non-stick ease. Take care to not press the mixture in tightly - press as gently as you can.

In a microwave-safe bowl, melt the peanut butter chips very gently, checking on them and stirring regularly to avoid scorching. When they have reached a very soft state, just stir them until they are completely smooth. Pour melted peanut butter chips over the Rice Krispies treats and spread to an even thickness with a spatula or back of a spoon. While peanut butter layer is still warm, work quickly to sprinkle the remaining chopped Oreo cookies over the top, followed by the remaining miniature marshmallows. Press the cookies and marshmallows into the peanut butter layer gently to adhere.

Allow treats to set for an hour before cutting into squares. Store in an airtight container.