Place lima beans in a large saucepan and cover with water. There is no need to soak them in water previously.
Cook lima beans at moderate heat. Boil for 5 minutes or until skin comes out easily.
Drain and skin remaining lima beans. Return to pan and cover with water. Return to heat until lima beans are soft and tender.
Drain and blend beans with the necessary amount of cooking liquid. Force through a fine sieve. Add butter and combine. Puree must have a soft and creamy texture. Season with salt and pepper.