The success of this extremely simple recipe depends on two things: the bread must be unsalted, country bread, a day or two old, and the rest of the ingredients must be top quality and fresh.
Leave the slices of bread to soak in cold water for half an hour. Clean the salad and vegetables and chop finely. Place in a salad bowl and add the fresh basil leaves. Using your hands, squeeze the bread thoroughly to remove the water and reduce to breadcrumbs. Add to the vegetables in the bowl and dress with oil, salt and vinegar. Toss well and leave in the fridge for an hour before serving.
There are several variations of this recipe, all of which add various other vegetables, but to me these seem a travesty of the real panzanella. You could, however, add cucumber and/or tomatoes, chopped or finely sliced, and a shake of pepper.
Choose the wine to accompany this dish with care as the vinegar will affect its flavour. In the past it was eaten with a weak, watery wine called vinello or acquerello, made by soaking the bunches of grapes left after the wine pressing in water and then squeezing them out. A light, young red wine is therefore best.