Making a timballo, or timpano, is an event. It becomes the moment in which ordinary ingredients like macaroni, cheese, and vegetables are transformed into an extraordinary, impressive drum of baked pasta that, when unmolded, receives a standing ovation. The region of Campania claims the timballo as its own and the recipe that follows comes from Sorrento. It calls for bucatini, a thicker cut of hollow spaghetti, which neatly nestles and holds the ingredients together. It is customary in Campania to use buffalo milk mozzarella, a cheese with a delicate texture and superb taste, but it is very perishable and not readily available. Fresh cow's milk mozzarella can be used instead. Assembling the timballo is easy when done in stages. Make the sauce several days ahead; cube the cheese and cook the marble-size meatballs 2 days ahead. Patience is the key to the unmolding; you will get much neater wedges by allowing the timballo to cool for about 20 minutes - and the joy of tasting that first forkful will be worthy of the best drumroll.