Line a 9×13-inch baking pan with aluminum foil and spray with nonstick spray and set aside. In a large pot, melt the butter over medium heat. Add in 8 cups of the mini marshmallows and stir until completely melted. Remove from heat.

Transfer the mixture to the prepared baking pan and spray a rubber spatula and/or your hand with cooking spray and gently press the mixture evenly into the pan.4 Top with additional Lucky Charms marshmallows and sprinkles if desired.

Make sure to keep your treats in an airtight container so they don’t get tough and dry out. Because they’re sticky, I recommend storing them in a container that allows you to keep them in a single layer OR simply cover the pan you made them in with aluminum foil or plastic wrap. They should be good for up to 3 days.