Heat oil over medium-high heat in a large saucepan. Add the onion and cook for 5 minutes or until the onion has softened. Add the garlic and cook for 30 seconds. Add the pumpkin, peanut sauce, chicken stock, and coconut milk. Bring to a boil, reduce heat and simmer for 5 minutes.
Puree the soup in a blender, working in batches, until smooth. Season to taste with salt and pepper.