Heat the butter and oil in a large, heatproof casserole and add the onion and garlic. Cook over a medium heat for 5–6 minutes until soft and golden.
Add the pumpkin and continue cooking for a further 8 minutes, stirring frequently, until beginning to soften and turn golden. Add the spices and cook for 2–3 minutes, making sure that the pumpkin is well coated.
Pour in the hot stock and bring to the boil, then reduce the heat, cover and leave to bubble gently for about 15 minutes until the pumpkin is soft.
Use a hand-held blender to liquidize the pumpkin until smooth, then stir in the spinach. Reheat for about 5 minutes until the spinach has melted and the soup is hot. Season to taste.
Spoon the soup into bowls, scatter over the lightly toasted pumpkin seeds and a drizzle of pumpkin oil and serve immediately.