Melt the butter in a large pot over low heat.

Add the marshmallows to the pot and stir until completely melted and smooth.

Gradually add the popcorn, mixing well to ensure each kernel is thoroughly coated with the marshmallow mixture.

Continue adding popcorn until you achieve your desired marshmallow-to-popcorn ratio.

Add sprinkles (optional)

Remove from heat, let cool slightly, then enjoy!