Add the butter to a large pan and begin to heat it on low heat.
While the butter heats, grease a 9 x 13 pan.
Add the marshmallows to the butter on low heat while continually stirring to avoid burning the mixture. Stir the mixture until it is all evenly melted.
Add the cookie butter and stir. Keep stirring the butter, marshmallows, and cookie butter mixture on low until it is completely melted and mixed together.
Add the rice cereal to the mixture and then pour everything into the 9 x 13 pan. Use a spatula to spread the mixture out evenly. Gently press into the pan. Let cool for about an hour before cutting into squares.