Heat oil and butter in a large saucepan. Add onion and sauté for a few minutes, until softened. Add garlic, pumpkin, cashew nuts and tomato paste. Cook gently for 2 minutes. Add chicken stock and bring to the boil. Reduce heat and allow simmering for 15 – 20 minutes, until pumpkin is tender. Place into a food processor and process until smooth. Season with nutmeg and cayenne and process for a few more seconds. Serve with a dollop of cream if desired, a sprinkle of chopped chives, some freshly ground black pepper and Chia seeds.