Spray a 9x13 pan with non-stick cooking spray and set aside. PRO TIP: Everyone always asks how I make rice krispie treats without all the sticky mess. Well, not only do I spray the 9x13 pan, I also spray the bowl AND my rubber scraper. It works so well- just watch the video above! No sticky marshmallow mess to clean!

Measure out rice Krispie cereal and set aside. Add regular mini marshmallows and butter to a large, microwaveable bowl. (I like to spray the bowl and a rubber spatula first with non-stick spray to make this entire process easier!)

Microwave for 1 minute on high, until marshmallows begin to puff up. Remove from microwave and stir in cereal. Once it's well incorporated, add in pastel mini marshmallows and M&M's. Stir until mixture is combined. Transfer to 9x13 pan and press gently into pan, making the top as level as possible.

Cool and cut into squares.