Gather 6 cups Rice Krispies cereal, 4 cups mini marshmallows, 3 tablespoons butter, and a 9×13-inch pan
Grease the pan
Melt the butter in a large pot over low heat
Add the marshmallows and stir until fully melted
Remove from heat
Add the Rice Krispies cereal
Stir until evenly coated
Press the mixture into the greased pan
Let cool until set
Cut into squares and serve
