Mix together popcorn, peanuts and raisins in a large bowl.
Coat a large glass bowl with cooking spray; add the marshmallows and butter. Cook on 70-80% power in the microwave until butter and marshmallows are melted, about 2-3 minutes, stirring halfway through. Immediately pour over the popcorn mixture and stir quickly. Spoon into an angel food cake pan coated with cooking spray.
Once cool, unmold and decorate with M&M’s.