Preheat the oven to 375°F. Fill a pot of water to boil on the stove.
Clean and peel potatoes. Chop potatoes and pumpkin into rough 2–3 cm cubes. Move cubes to boiling water. Return pot to boil and cook for 15–20. Cubes should be tender.
Gently fry diced onion in a small amount of oil until it is soft and slightly browned (but not caramelized).
Drain potato and pumpkin. Mash them until they form a smooth paste uing a potato masher. Mix in fried onion and chives.
Add hoisin sauce and soy sauce to taste. Set filling aside.