Line a large baking sheet with foil or parchment paper, then butter or spray with cooking spray; set aside.

Measure out 20 cups of cereal into TWO large bowls, dividing evenly; set aside.

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

Once melted, stir in 2 bags of Jumbo marshmallows, melt, stirring often.

When melted, stir in 2 bags of Mini marshmallows and remove from heat. (The marshmallows will not be fully melted)

Stir in salt and vanilla.

Pour melted marshmallow mixture evenly over BOTH bowls of cereal.

Working quickly, use a rubber spatula to fold and mix the cereal and marshmallow mixture until all cereal is thoroughly coated.

Pour all coated cereal onto the prepared baking sheet.

Wet your hands with cold water, shaking off the excess, and press the cereal mixture firmly and evenly into pan.

All this to cool and firm up. (I place mine in the refrigerator for 30 minutes or so for faster results)

Lift out of the pan using the sides of the foil and cut into desired size squares.