Heat the oil in a large saucepan over medium heat. Add the parsnips and onion and cook for 5 minutes. Add the curry paste and cook, stirring, for 1 minute. Pour in 500ml (17fl oz/2cups) of the stock.
Cover, bring to the boil, then simmer for about 20 minutes, or until the parsnips are tender. Cool slightly, then transfer to a food processor and blend until smooth. Return to the saucepan, stir in the remaining stock and the cream. Season well and serve hot with crusty bread.