Lightly mist a 9-inch by 9-inch square baking pan with non-stick spray.

Place 5 cups of the mini marshmallows in a large pot, along with the butter and salt.  

Cook over medium-low heat, stirring, until melted and combined (3 to 5 minutes).  

Stir in the rice krispies.  

Remove from the heat and allow to cool slightly (about 5 minutes).  

Stir in the remaining mini marshmallows.

Transfer the mixture to the prepared pan, pressing lightly with your fingertips to shape.  Cut into bars and serve.