Preheat the oven at 375ºF and place the oven racks in the middle.
Carefully cut each squash in halves or quarters.
Slather each piece of squash with butter, sprinkle generously with Celtic sea salt, place on a baking sheet skin sides down, and place in the oven.
Roast for about an hour or until the squash is tender throughout.
When the pumpkin/squash are cool enough to handle, scoop it into a large pot over medium high heat.
Add the coconut milk and curry paste and bring to a simmer.
Remove from the heat and puree with a hand blender; you should have a very thick base at this point.
Add water a cup at a time, pureeing between additions until the soup is the consistency you prefer – a light vegetable stock would work here as well.
Bring up to a simmer again and add the salt (and more curry paste if you like).