Heat olive oil in a large pan over high heat. Add prawns and cook for two minutes on each side. Season with salt and pepper. Add shallots and garlic and cook over medium heat 1-2 minutes. Add cannellini beans and remove from the heat.
Mix dressing ingredients in a small bowl until combined and add to prawn mixture. Add chives, witlof and celery, toss gently and pile onto a platter.