Heat the oil in a frying pan. Saute onion over medium beat, stirring gently for 5 minutes or until lightly browned. Add pumpkin and saute for 2 to 3 minutes more. Add water to cover, bring to the boil and cover pan. Reduce heat and simmer for 30 minutes or until tender. Add water during cooking if necessary to prevent burning.
Thin the miso with 120ml water and add to the pumpkin. Simmer until dry.