Remove the seeds and stringy fibres from the pumpkin and cut into 2-cm chunks. If you use kabocha pumpkin/buttercup squash, you don't need to peel it!
Place the pumpkin and dashi in a large saucepan and add the shoyu, mirin, sugar and sake.
Bring to a boil over medium heat, then turn the heat down to low and simmer for about 15 minutes, until the pumpkin cooked.
Take the pumpkin out of the stock and serve, hot or cold, with rice. Keep the broth to simmer other vegetables, such as potato, daikon, or sweet potato.
Recipe by Kiku Corner at https://www.kikucorner.com/2015/04/08/kabocha-no-nimono-japanese-simmered-pumpkin/