Cut the squash in half lengthwise, scoop out the seeds, and peel the outside with a vegetable peeler. Chop the squash into about 1 inch chunks. Put the squash in a pot, add the salt, 1 Tb. butter and enough water to just cover the squash. Bring to a simmer and cook, covered, until the squash is tender about 10 to 15 minutes. Add the ginger and garlic to the squash during the last three or four minutes of cooking.
Puree the squash, either in a blender or with a hand-held stick blender. If using a blender, drain the squash first, but reserve the cooking liquid, then add it back to the pureed squash.
Add the remaining 2 Tb. butter to the pureed squash, and if desired, add the heavy cream. Season to taste with salt and pepper, garnish with parsley and/or chives. This recipe may be prepared in advance, and the soup may be frozen without the heavy cream.