Peel and dice the onion and ginger. Heat some oil in the saucepan and sweat the onion in it. Add the pumpkin cubes and the ginger and sauté briefly. Pour in the water, add the stock and cook everything until the pumpkin is cooked through.
Take the pot off the stove and puree everything well with a hand blender. Add the cream, stir and bring to the boil again briefly. Season to taste with salt, pepper and cayenne pepper.
Cut the chives into small rolls and add to the soup before serving. Serve with toast or baguette.