1Place the squash halves, cut sides up, on a large plate or dish. Cover and microwave with 650 watts for 6 minutes, or until very soft. Set aside until cool enough to handle.
2Place onion, ginger, coriander, allspice, salt, butter and 3 cups water in a large bowl. Cover and microwave with 650 watts for 10 minutes. Remove the ginger pieces.
3Scoop the pulp out of the squash halves and add to the spice mixture. Purée the mixture in a food processor or food mill, then return it to the bowl. Cover and microwave with 650 watts for 6 minutes, or until heated through. Stir in the lime juice and cream, sprinkle the cilantro over the top, and serve hot.