Line an 8 x 8 baking dish with parchment paper and set aside.
Add butter to a medium stock pot over low heat until melted. Then add marshmallows. Continuously stir with a wooden spoon until melted, about 5 minutes.
When the marshmallows are fully melted, remove from heat and mix in brown rice crisp cereal. The mixture will be very sticky. Then add Natural SunButter. Mix until evenly distributed and well combined.
Pour the rice krispy mixture into the lined pan and press down with an additional sheet of parchment paper, until flat on top. Let cool completely.
Once cooled (about 10 minutes), cut into 9-12 squares and serve. Store in an air-tight container. Enjoy!