1Melt the oil in a large saucepan and add the curry powder - cook for a minute or so, until the curry powder has formed a paste and smells aromatic.
3Add the leeks, potato and apples to the curry mixture and sauté for about 5 minutes, over a gentle heat making sure the vegetables and fruit.
5Add the stock and then cover with a lid and simmer for 20 to 25 minutes. Adjust seasoning with salt and pepper and then transfer the soup to a food processor or liquidiser and blend until smooth.
7Return the soup to the saucepan and reheat over a gently heat, making sure the soup doesn't boil.
9Serve the soup in warmed soup bowls, with a swirl of yoghurt over the top and some snipped fresh chives as a garnish.