Gather your ingredients: marshmallows, butter, cereal, and any fun add-ins you want to include.
Melt the butter in a large saucepan over low heat, stirring gently until it becomes shiny and smooth, filling your kitchen with a rich, buttery aroma.
Add the marshmallows to the melted butter, stirring constantly until they melt completely and the mixture is gooey and bubbly, with a sweet, marshmallow scent wafting through the air.
Remove the pan from heat once the marshmallow mixture is smooth and bubbling, ready to be folded into the cereal.
Pour the marshmallow mixture over the rice cereal in a big bowl, then gently fold everything together with your spatula until the cereal is evenly coated and sticky.
If desired, sprinkle in chocolate chips or candies now, folding lightly to distribute them throughout the mixture.
Grease your 9x13 inch pan lightly with butter or spray, then transfer the mixture into it, pressing down firmly with a spatula or wax paper to create a packed, even surface.
Allow the treats to cool at room temperature for about 30 minutes, during which they will firm up and set into big, chewy squares with crispy edges.
Once cooled, use a knife or pizza cutter to slice the treats into monster-sized squares, revealing their sticky, crunchy texture and colorful mix-ins.
Decorate your monster Krispies with edible eyes, fangs, or sprinkles to bring your playful creature to life—get creative and have fun!
Serve your monster Krispies on a plate, enjoy the crunchy-chewy bites, and share the chaos and fun with friends or family!
