In a large saucepan over medium heat melt the butter. Add the rest of the marshmallows and the salt. Stir into the butter over medium heat until the marshmallows are completely melted and incorporated with the butter.
9 cups mini marshmallows, ½ teaspoon salt, 5 TB butter
Pour the melted marshmallow mixture over the cereal mixture and gently stir until fully coated/combined.
Spread the mixture into a 9x9 inch (or similar sized) pan and press gently with a spoon or spatula to flatten the top.
Allow to cool in the pan for 30 minutes before slicing and serving.