Prepare 10 cups of popped popcorn and place in bowl.
Melt butter and marshmallows on the stovetop until melted.
Pour 2/3 melted marshmallow over the top of the popcorn and stir until coated. Pour popcorn onto a parchment covered cookie sheet and spread out.
Pour remaining 1/3 marshmallow over the popcorn evenly and sprinkle with topping. Work quickly so that toppings stick to the popcorn!