1. Assemble a solar cooker with a black glazed clay pot with lid in a bigger glass bowl with lid. Place the bowls on a reflector.
2. Butter the black glazed dish.
3. Add the remaining butter and marshmallows in the bowl and let it stand in the sun for 1 and half hours checking in between to see if the marshmallows have melted in a cream.
4. Stir in the butter and marshmallows well.
5. Remove from heat and empty the rice cereal into it.
6. Mix well and take a bigger rectangular dish and grease it.
7. Add the mixture of the marshmallows and the cereal in the rectangular dish and press it with a spatula so that it assumes uniform thickness.
8. Cut out with a knife into medium sized squares and serve.