Peel the ginger and onions and cut into narrow strips, briefly toast with the butter in a saucepan.
Cut the sweet potato and pumpkin into small pieces (Hokkaido pumpkin does not need to be peeled!). Add to the pot with the water and cook together for about 20 minutes until the vegetables are soft.
Add the spices and cream and use the hand blender to puree all the ingredients to make a creamy soup.
If you like: serve with pumpkin seed oil, pumpkin seeds and a dollop of sour cream on the plates.