Rinse the prawns in a sieve and drain well.
Peel the oranges, removing the white pith.
Halve the oranges and cut into thin slices.
Wash and slice the celery.
Cut the celery into slices.
Peel and finely dice the ginger.
Dice the ginger finely.
Place the mustard in a bowl and mix with the ginger and sugar.
Add the oil, a spoonful at a time, and stir until smooth.
Squeeze the remaining orange and add the juice to the dressing.
Season with salt and pepper. Add the vinegar.
Chop the celery leaves.
Add to the dressing, stir and taste.
Wash the basil, shake dry and slice the leaves.
Peel and finely dice the onion.
Cut into fine cubes.
Wash the iceberg lettuce, shake dry and tear into small pieces.
Arrange the orange slices, celery, basil and prawns on plates. Drizzle over the dressing.