To mash or puree fresh pumpkin, place a whole, uncut pumpkins on a foil-lined baking sheet. Bake at 350 degrees for 90 minutes or until tender, turning the baking sheet occasionally. Remove the pumpkins from the oven, and let cool.
To clean pumpkins, cut them in half vertically and remove the seeds and stringy pulp with a large spoon. Scoop out the flesh with a spoon, and place it in a bowl, being careful not to get any of the softened skin in with the flesh. Discard the skins. Mash the pumpkin with a potato masher, or, use a food processor if you want an even smoother texture.
You can store fresh cooked pumpkin purée in a sealed container in the refrigerator for about 5 days, or in the freezer for up to six months.