In a large pot or stockpot, sautee onions in oil and butter until tender.
Add minced garlic and cook another minute.
Add the pumpkin, chicken stock, brown sugar, salt and spices.
Cover and simmer 20-25 minutes.
Blend the soup using an immersion blender or in batches in a regular blender.
Return the mixture to the pot and add the heavy cream.
Cook for 5-10 minutes.
Garnish with toasted pumpkin seeds, croutons and/or drizzle of heavy cream.