Arrange the slices of duck on a bed of lettuce on a serving dish. Sprinkle over the shallots, spring onions and cucumber and celery, if you want.
To make the dressing, put the fish sauce, lime juice, garlic, chillies and sugar into a small pan, and heat through gently. The actual amount of ingredients is just a guide and you can experiment until it is to your liking. Pour the warm dress