Line a 9x9 baking dish with parchment paper and spray with non-stick cooking spray.

Pop the corn and melt white chocolate in the microwave in 30-second increments, stirring in between, until smooth and creamy.

In a large bowl, drizzle melted white chocolate over popped popcorn and mix and dust with a little salt. Mix everything together until the chocolate evenly coats the popcorn.

Melt the butter in a large saucepan over medium high heat. Add the marshmallows and continuously stir to combine until the marshmallows are melted and smooth.

Stir in the popcorn and and mix until the popcorn is well coated. Then stir in 2/3 of the M&Ms. Immediately transfer the mixture into the prepped baking dish pressing it firmly into an even layer. I like to use parchment to do this. Sprinkle with remaining M&Ms and more sprinkles on top.

Let it harden for about 20 minutes and then cut and serve. I like it best when served right away.