First start by lining an 8x8 inch baking pan with parchment paper then set aside.
Microwave method
In a large bowl melt the 10 ounces of marshmallows in the microwave for 30-60 seconds or until fully melted. Add in the melted butter and melted peanut butter and stir until combined. Add in the Rice Krispies and gently fold until halfway coated. Add in the mini marshmallows and gently fold.
Gently spread the mixture in the prepared baking pan without pressing too hard and let it set for 30 minutes before cutting into it.
Stove top method
Melt the butter in a large pot over medium heat. Add in the 10 ounces of marshmallows, turn the heat down to low, and stir until melted.
Remove the pot from the heat, add in the peanut butter, and stir to combine, then mix in the Rice Krispies until almost fully coated. Fold in the remaining mini marshmallows.
Gently spread the mixture in the prepared baking pan without pressing too hard and let it set for 30 minutes before cutting into it.