To make the dressing: Place vinegar, oil & fennel seeds into a small bowl & mix to combine.
Preheat a barbeque or grill plate over a high heat. Peel & devein the prawns, leaving the tails intact. Brush the bread & prawns with oil, rub with garlic & season with salt & pepper. Cook for 2-3 minutes each side or until bread is charred & prawns are cooked through. Allow to cool slightly.
Place cucumber, onion, tomatoes, prawns & bread into a bowl, season with salt & pepper & pour over dressing. Toss to combine & allow to stand for 10-15 minutes. Top with fresh basil to serve. Serves 4