Peel and chop the onion, dice the vegetables.
Heat the oil in a large pan and cook the onion for 5 mins until just softened. Add the curry powder and stir for a minute to coat well. Add the diced vegetables, cover and gently sauté for 5-8 mins.
Pour in the vegetable stock, bring to the boil, then reduce the heat and simmer for 25-30 mins until the vegetables are tender.
Using a stick blender whizz until you get a smooth, velvety soup.
Season to taste with salt and pepper.
Serve with a dollop of yogurt, if liked, or some chopped coriander leaves.