Heat the oil in a saucepan and gently fry the spring onions for 5 minutes over a medium heat until softened.
Add the spinach, peas and broccoli and pour over the stock. Bring to the boil and season with salt and pepper, then reduce the heat and simmer for 10 minutes until the veg is tender.
Add most of the mint leaves and blitz until smooth, either using a hand-held stick blender or by transferring to a food processor. Serve topped with mint leaves and a scattering of feta.