Melt butter in a stock pot on low heat , once butter melts add in a bag of mini marshmallows, fold in the marshmallows as they start to melt, then add in the 8 cups of cereal and add an extra cup of marshmallows (optional) remove pot from heat, if your adding in any extras do it at this time. Fold all ingredients in together, mixture will be very sticky, once blended transfer to your already greased 13 x 9 rectangular pan.