With a heavy knife, cut the top from the squash, just below the skin. Now cut down through to cut squash in half. Scoop out the seeds and loose fibers, Next quarter each half and remove green skin.

Put the large pieces of squash in a large saucepan with 1/4" of water and bring to a boil. Reduce heat to a full simmer and cook for about 20 minutes or until squash is tender to fork. Pour off water and turn off the burner. Put 2 tbsp. of butter or margerine on the squash. Let squash sit in the pan on the burner for a few minutes. Mash the squash and season with salt and pepper to taste. Whip the mixture if you want a finer puree.