Line a 9x9 inch pan with parchment paper, leaving some overage on two ends.
In a large pot, melt peanut butter, chocolate chips, and butter over medium low heat until just melted.
Remove from heat and cool slightly. Add mini marshmallows and crisp rice cereal.
Stir until the chocolate sauce covers the marshmallows completely.
Fold into prepared pan. Cool completely. I refrigerate so the bars are completely firm before slicing.
Using a knife, cut along the edge without the parchment paper to loosen from the side. Then using the parchment paper on each end, pull the squares up and out of the pan.
Place onto a flat surface or cutting board. Using a sharp knife, cut into desired sized pieces.