Combine butter and 8 cups marshmallows in a microwave-safe bowl. Cook for 1- 2 minutes or until the butter and marshmallow are just melted, no longer.

Stir in vanilla extract.

Add cereal and stir, followed by the remaining 1 cup of marshmallows. Continue to stir until the cereal is well coated.

Grease a 9x13" pan and spread ½ of the cereal mixture into the pan, pressing with just barely wet hands to make it easier.

Place spoonfuls of the marshmallow cream over the entire top of the layer of cereal and spread to cover.

Press remaining cereal mixture over the marshmallow cream and press into an even layer.

Let cool and set for about an hour before cutting.