Step 1 Heat the oil and butter in a large heavy-based saucepan over a medium heat. Add the onion and garlic and sauté for 5 minutes or until soft. Step 2 Add the zucchini and stock and bring to a gentle simmer. Cook for about 10 minutes, partially covered, until the zucchini has softened but still holds its shape. Step 3 Add the sour cream and basil and use a stick blender to blend until the soup is a smooth consistency. Season with freshly ground black pepper and salt to taste.
