Peel the cooked prawns and decide how you want to present them... for example you can split them almost in two as in the photo above, and create attractive 'butterflies' with them. Or you may wish to do what I do which is to remove the head and the shell, but leave the tail on. I then cut through the prawn from the underside almost to the back, but not quite. I can then 'flatten' them out so they are very thin and each prawn has two 'sides' showing (a bit like the photo above but without cutting right through the prawn).
So prepare your prawns as you feel right and lay them out on four plates. Dare to be inventive with your prawn arrangement. Remember, a good meal starts with what you see and smell, not what you taste. The important think is that the prawn must be peeled so that the vinegar and oil mix permeates the flesh.
In a small bowl, mix together the oil and lemon juice. Finely chop the basil leaves and add to the oil mix. Drizzle this mixture over the prawns and place them in the fridge for an hour to allow the marinade to work. Remove from the fridge and serve with crudités (sliced or whole raw vegetables, possibly including celery sticks, carrot sticks, bell pepper strips, broccoli, cauliflower, asparagus spears) accompanied by a little mayonnaise to dip the crudités in.