Heat the oil and butter in a large saucepan over a medium heat.
Add the leeks and garlic, and cook for 5-7 minutes until softened.
Add the potatoes and vegetable stock, and cook for 15mins or until the potatoes are done.
Save a handful of peas for the garnish, then add the remaining peas and the mint to the pan, and cook for a further 5 mins.
Season with salt and pepper.
Blend until smooth in a blender or food processor.
Serve drizzled with olive oil and sprinkled with croutons, the reserved peas and the pea shoots.