Marshmallow Popcorn - Quick, easy and doesn't stick to your fingers! 3 bags microwave popcorn, popped and unpopped kernels removed. 2 sticks of butter 16 oz bag of mini marshmallows 1 C brown sugar Microwave butter, marshmallows, and brown sugar for 2 1/2 min. Take out and stir. Microwave again for 1 minute. Repeat until all is melted. When done pour over popcorn and mix. YUM!