Remove skin and seeds from pumpkin and cut into even sized chunks.
Heat oil and butter in a large saucepan over medium high heat. Add onions and cook 1-2 minutes or until onions have softened. Add pumpkin and cook for a further 3-4 minutes, stirring occasionally. Add the stock and bring to the boil. Reduce heat to medium low and cook, covered for 30 minutes. Remove from heat;cool slightly.
Using the StickMaster, process until smooth.
Reheat until soup is hot. Serve with cream and extra ground black pepper if desired.