Line 2 (8x8) cake pans with foil and spray with non-stick cooking spray. Set aside.

In a large pot, melt the butter over medium heat.

Stir in 9 cups mini marshmallows and continue to stir until smooth.

Remove from heat and stir in cereal.

When almost finished mixing in cereal, add in the 4 cups mini marshmallows and stir to combine.

Divide evenly between two pans and press down.

Allow bars to cool before cutting.

Enjoy!