1In a large heavy saucepan, bring the leeks, potatoes, water, and salt to the boil over high heat.
2Cover partially, reduce heat, and simmer for 20 to 30 minutes until the vegetables are tender.
3Correct the seasoning, to taste, and puree with a handheld immersion blender, or in batches in a food processor.(I personally like to use a laddle and scoop up soup, putting in a food processor then making it into pureé).
4Whisk in the cream and reheat before serving. Top each serving with a sprinkling of fresh chives and/or parsley.