In a saucepan over medium heat, combine the corn syrup, butter, powdered sugar, marshmallows, salt, and vanilla.

Stir frequently until mixture comes to a boil.

Add 2-4 drops of green food coloring (depending on how dark you want the color to be) and stir well.

Pour the mixture over the popcorn, mixing well to ensure each kernel is coated.

Grease hands with shortening and quickly shape the coated popcorn into balls before it cools.

To store, wrap each ball in plastic wrap and keep at room temperature.