Measure cereal and place in a large bowl.
In a microwavable bowl, microwave white chocolate chips, peanut butter and coconut oil on high for 30 second intervals, stirring between each, for no more than a total of 90 seconds.
Stir until smooth. Stir in mint extract and green food coloring.
Pour mixture over cereal, stirring until evenly coated. Sprinkle with nonpareils if desired.
Pour into a 1 gallon resealable bag.
Add powdered sugar. Seal bag and shake until well coated.