Cover beans with water; add chopped onion and bring to a boil.
Boil 2 minute.
Take off heat, cover and let sit 1 hours.
Do not drain water, but again add enough water to cover beans, heat to boiling, turn down heat and cook until beans are tender, stirring occasionally, about 1 to 2 hours.
(add more water if needed during cooking) When beans are done (make sure there is not too much water in the beans), take off heat and mash with a mixer Add margarine, salt, pepper, and cheese and continue to beat with mixer until the beans are soft.