Finely chop the garlic and mix in a bowl with a tablespoon of oil, generous pinch of salt, pepper and the juice of the lime. Add the prawns and leave to marinade for about 5-10 minutes.
Pre-heat the BBQ over a medium heat for 2-3 minutes, then fry the prawns with the marinade for 2-3 minutes. Remove from the pan with a slotted spoon and keep the heat on low.
For the dressing, add the balsamic to the pan and warm through.
Divide the lettuce, nectarine and prawns between two plates and drizzle over the dressing before serving.