Melt the coating. In a large pot, melt the butter over medium-high heat. Once melted, add the marshmallow fluff and 1/2 cup of chopped chocolate candy bar. Melt and mix until smooth. Remove from heat.
Combine. Using a large rubber spatula, fold the popcorn into the fluff mixture. Once all the popcorn is evenly coated, add some candy-coated chocolates.