Prepare a baking pan by lining it with parchment paper or lightly greasing it; set aside.

If not already chopped, chop the 116 oz package of Nutter Butter Cookies and set aside.

In a large saucepan over low heat, combine the 1/2c. butter and 1/2c. peanut butter. Stir constantly until melted and smooth.

Still over low heat, add the 210.5 oz bags mini marshmallows to the butter and peanut butter mixture. Stir continuously until the marshmallows are completely melted and the mixture is smooth.

Remove the saucepan from the heat immediately.

Add the 6c. rice krispie cereal and the chopped 116 oz package of Nutter Butter Cookies to the melted marshmallow mixture. Stir gently but thoroughly until the cereal and cookies are evenly coated.

Transfer the mixture into the prepared pan. Using a spatula or the back of a spoon (you can lightly dampen the spatula or press with parchment to prevent sticking), press the mixture firmly and evenly into the pan.

Allow the bars to cool for about 20–30 minutes at room temperature until set.

Once cooled and set, lift from the pan (using the parchment if used) and cut into squares.