In a large sauce pan, melt butter and marshmallows together. Once melted mix in vanilla.

Remove from heat and fold in the popcorn and graham cereal until well coated.

When it is cool enough to handle, sprinkle the mixture with the mini chocolate chips.

Spray hands with non-stick spray and shape into 1 cup sized popcorn balls.

Place on a sheet of waxed paper or parchment paper to cool fully. Store in a sealed container until serving. Makes about 10 popcorn balls.