01 -
Grease a 9" x 9" pan with butter or nonstick cooking spray. You can also line it with parchment paper if you're concerned about sticking. Note that a square pan will make thicker treats, while a rectangular pan will result in thinner treats.
02 -
Spray a large mixing bowl with cooking spray and add the marshmallows. Microwave in 30-second increments until they're melting and puffy. Alternatively, you can melt them in a large saucepan over the stove.
03 -
Add the butter and salt to the melted marshmallows. Stir until completely melted and combined. For easier mixing, grease your spatula with cooking spray or oil to prevent sticking.
04 -
Reserve a few of the colorful Lucky Charms marshmallows for topping. Add the Lucky Charms and Rice Krispies cereals to the melted marshmallow mixture one cup at a time, stirring to combine after each addition.
05 -
Pour the cereal mixture into the prepared baking dish and press it into an even layer using a spatula. For best results, coat your clean hands with cooking spray and use them to press the mixture firmly into the corners.
06 -
Sprinkle the reserved Lucky Charms marshmallows on top while the treats are still warm. Let them rest in the pan until they come to room temperature, or freeze for 20 minutes to set up quickly.
07 -
Release the edges of the treats with a knife, then remove them from the pan and cut into 9 equal squares. Enjoy immediately or store for later.