Heat the oil in a large saucepan, and add the onion and garlic. Cook over a medium-low heat for 5 minutes, stirring regularly, until fairly soft.

Add the peas, broccoli, and asparagus, and then pour over the vegetable stock. Season with plenty of black pepper.

Bring to a simmer, and cook for around 15 minutes, until the vegetables are tender but still bright green.

Add the chives and spinach, and cook for a further 1 minute, until the spinach has wilted.

Blend the soup until smooth. Add the Greek yogurt, and mix to combine. Serve topped with any extra yogurt and chives.