In a small saucepan, combine pumpkin, onion, butter, brown sugar, salt, and pepper. Cook, uncovered, over medium-low heat for 15 minutes, stirring occasionally.
Meanwhile, place potato chunks in a medium saucepan. Add enough water to cover. Bring to boiling; reduce heat. Cover and cook about 15 minutes or until potatoes are tender.
Drain off potato liquid, reserving potatoes and 1/3 cup liquid in pan. Add pumpkin mixture and cream cheese to potatoes and liquid in pan.
Mash with a potato masher, leaving potatoes slightly chunky. Stir in chives. Cook and stir over low heat until heated through. Serve immediately. Makes 6 servings.