In a large microwave safe dish combine pumpkin, onions and butter. Cover and microwave on high for 4 minutes.
Peel pumpkin. Stir in stock and cook on high for another 20 to 25 minutes or until pumpkin is tender.
Puree pumpkin, onions and stock in a food processor or blender. Add cream, salt and pepper, and microwave on high for another 3 to 4 minutes, or until heated through. Flavour with nutmeg, cloves and cinnamon to taste.