I'v been making these for desert since I was 6 and the best part is they still taste GREAT.
Put a 1/4 a stick of butter with some marshmallows in a bowl & heat in microwave or oven.
Poor some classic Rice Krispies on top (poor alot for crunchy, poor alittle for more gooey)
Put them in a brownie pan (place whatever topping you enjoy)
Cut them up.