Pre measure all ingredients and have them ready. Spray or butter a sheet pan.In a large pot (dutch oven, stock pot etc) melt butter over medium high heat. When melted add all of the Jet Puffed marshmallows. Stirring constantly melt over heat into the butter. Once this is melted and smooth, remove from heat. Stir in vanilla. Then add cereal. Stirring gently but quickly coat the cereal completely in the marshmallow mixture. Add ½ cup of the mini marshmallows just before pouring on the sheet pan and stir a few times. Then sprinkle ½ cup of the mini marshmallows on the sheet pan. Pour cereal mixture on to the sheet pan. Spray hands with spray and working quickly adn gently lightly spread to edges. Careful on to mash down the mixture or you will end of with tough treats. Sprinkle 1 cup of the topping marshmallows and sprinkles and let sit for about 15 -20 minutes. Slice into 35 squares!