In a large saucepan over medium-low heat, combine 6 tbsp butter and 6 cups of mini marshmallows. Stir continuously until melted and smooth.
Pour in the Rice Krispies and stir to combine, then add the remaining mini marshmallows and mix until evenly distributed.
Lightly wet your hands and then scoop approximately 1/3 cup of the mixture and roll the Rice Krispies treats into a tight ball. You will need to rewet your hand every few Rice Krispie Treat balls to keep them from sticking to your hands.
In a microwave safe bowl, combine the chocolate chips, peanut butter and the remaining 2 tbsp of butter, then microwave in 30 second intervals, stirring in between, until melted and smooth.
Transfer the Rice Krispie balls into an extra large bowl and pour the chocolate peanut butter mixture on top. Stir to coat them in the chocolate peanut butter mixture.
Once coated, roll each ball into powdered sugar before enjoying! If you want the chocolate coating to be more set, refrigerate for 15 minutes.