In a small saucepan, melt peanut butter and butter on low heat and mix well.
Take it off heat once you get a smooth silky texture
In a large bowl, add the rice crisps and confectioners' sugar and mix
Pour in the peanut butter mix while it is still warm
Mix with a spatula or your hands till everything mixed well
If the mix is too wet, add more confectioners' sugar. If its too dry, pour in more peanut butter + butter mix.
Once mixed thoroughly, refrigerate for 15 minutes
Line a baking tray with parchment paper.
Take off a 1 inch scoop (or a small cookie scoop) from the mix
Roll into balls and put back on the tray and refrigerate for 1 hour or up to a day (if you want to make ahead)