Add marshmallows and stir until melted and well-blended.
Cook 2 minutes longer, stirring constantly. Remove from heat.
Use a buttered spatula or waxed paper to press the mixture evenly and firmly into a buttered 13 x 9-inch pan.
Cut into 2 x 2-inch squares when cool.
Notes
Feel free to experiment with the recipe to find the best consistency for you.If you want crunchier bars, remove a tablespoon of butter, or if you want gooier bars add a tablespoon of butter.