Peel the kabocha squash, cut into 1-cm thick slices, place in a microwavable dish, cover with plastic wrap and microwave for about 2 minutes (approximate time needed to cook 2 portions). Blend the kabocha squash with the water in a blender.
Add the water to the (A) glutinous rice flour and knead until it has the consistency of an earlobe. Divide the dough into portions to make 3 dumplings per person, roll each into a ball and boil in water. When they float to the surface, transfer to cold water and drain. Heat the (1) kabocha squash mixture and add the sugar and the salt. Place the dumplings in a bowl, ladle the kabocha sweet soup over them and serve.