Bring water, bouillion cube, and desired amount of crab boil to a boil in a saucepan. You can always start on the lower end of crab boil & adjust up. Remember that some of the heat will "cook off" when you add broth to squash later. Boil for 10 minutes.
Meanwhile, coursely chop squash and onion. I don't peel my squash, but you can peel them if desired before chopping.
Put squash and onion into a dutch oven and pour broth mixture in over vegetables. Cover vegetables about 2/3 of the way, don't completely cover (you may have some broth left over). Bring to a boil and simmer for 20 minutes. When squash is tender, remove from heat & let cool.
When cool enough to handle, transfer squash mixture to a blender or food processor and blend until smooth.
Return squash mixture to dutch oven and slowly stir in cream. You might not want the whole cup. Season with salt and pepper to taste. Add dash of cayenne pepper, if desired.
If planning to serve cold, let stand in refrigerator several hours or overnight to allow flavors to blend. Stir well before serving.
If freezing, let cool completely, then place desired number of servings in freezer containers. Freeze for up to 3 months. To prepare from frozen, simply thaw in microwave or stovetop & serve!