Bring one litre of water in a large soup pan to a boil. Wash the butternut squash, remove the seeds from the bulbous part and slice the flesh, leaving on the skin. Peel the sweet potato and cut it into pieces. Add both the squash and sweet potato to the pan and cook until tender.
Clean the ginger by scraping off the peel or peeling it thinly, and cut the ginger into pieces. Add the ginger, coconut milk and vegetable stock cubes to the squash and sweet potato.
Halve the papaya, carefully removing the seeds with a spoon. Peel the papaya, and cut half of it into small cubes for garnishing. Leave the other half whole and mash it into the soup. Once the vegetables are cooked, add half the papaya and puree the soup with a hand blender, food processor or blender. Season to taste with sea salt. Taste.
Pour the hot soup into bowls and garnish with chopped spring onion, olive oil, lime juice, coarsely ground pepper and the diced papaya. You can also add sesame seeds or chili pepper. Optionally, serve the soup cold after refrigerating for at least 2 hours.