Place the butter and the marshmallows in a microwave safe bowl. Microwave for 30 seconds. Remove bowl from microwave.
Stir in the crispy rice cereal.
Transfer to small lightly buttered dish. Gently press down with the back of a spoon. Cool before eating.
Notes
Prompt Removal of Marshmallows: As soon as the marshmallows are melted, take them out of the microwave. Overcooking can cause them to harden and thicken, affecting the texture of the treat.
Gentle Stirring: When combining the cereal with the marshmallows, stir lightly. Crispy rice cereal is fragile, and vigorous stirring might break the pieces, altering the treat's texture.
Soft Pressing into the Pan: Press the mixture into your pan softly. The goal is to have a gooey, light treat, not one that's overly firm and compact.