Can be made earlier in the day. Snip off the tops, but not the curly tails (they look better rustic-style), from the green beans. Boil in salted water for 3 mins until just tender. Get a bowl of iced water ready. Drain the beans and plunge into the water for 3 mins, then drain well and tip out onto a plate. Finely chop the shallot, scatter over the beans and sprinkle with some vinaigrette. Set aside to cool.
Chop a shallot like a proPeel, but leave some of the root end attached. Slice in half lengthways and place, cut-side down, on a board. Using a razor-sharp knife make several slashes from the tip almost to the root. Then cut twice into the flesh at right angles. The flesh will start to splay out. Pull the flesh in and hold together with your fingers. Bring the knife up and down at right angles, chopping the flesh into fine dice.