2) Bring another pan of salted water to the boil and throw the beans in just for a minute or two until they turn bright green. Strain and run the beans under cold water to stop them from cooking further.
3) In a mixing bowl combine the remaining ingredients, except the parsley, and whisk until smooth.
4) Cut the potatoes in half lengthwise and then into roughly 2cm chunks. Cut the beans in half. Toss the potato chunks in the dressing and then toss in the green beans and the parsley.