Melt 1 tbsp. butter in a large skillet or pot over medium heat. Once butter is melted, add in mini marshmallows and stir until marshmallows melted - careful not to burn. Remove from heat. Add in popcorn then fold in peanuts.
Line a baking sheet with parchment paper. Pour mixture onto baking sheet and spread as much as possible with spatula. Refrigerate for at least 5 minutes. Meanwhile, melt chocolate in microwave for about 1-1 ½ minutes on high or until melted and spreadable.
Once cooled, break into popcorn mixture into 12 pieces/clusters. Drizzle with melted chocolate. Chill for additional 10 minutes or until chocolate solid. Enjoy!