Add mini marshmallows and salted butter to a microwave-safe mug or bowl and microwave on high for 20-30 seconds. Marshmallows double in size and may bubble over the mug, so if you have a larger mug, that might work better.
Carefully remove the mug and stir well until butter is completely melted and mixed with marshmallows.
Add Rice Krispie Cereal and mix well until evenly coated. Enjoy while warm!
Substitute butter for peanut butter!
Use fresh marshmallows.
Try this breakfast of champions with other cereals – like Cinnamon Toast Crunch, Cheerios, or Fruity Pebbles.