In a large sauce pan, melt 3 Tbsp of butter over medium heat.
Step 2: once the butter is completely melted, add a large bag of marshmallows. Stir until the marshmallows are completely melted. They should look like a liquid cream and be very easy to stir.
Step 3: At this point, you can add your cereal. Stir in 6 cups of Rice Krispies original cereal. It will become thick and difficult to mix.
Step 4: once the cereal is coated well with the marshmallows, spray a large pan with non-stick cooking oil. Pour the mixture into the pan, and with a buttered spatula, flatten it out.
Step 5: cut, decorate and enjoy! :)