ASK AN ITALIAN about Italian cooking and, depending on whom you approach, you will be told about Bolognese, Venetian, Roman, Milanese cooking or Tuscan, Piedmontese, Sicilian, Neapolitan. But Italian cooking? It would seem no single cuisine answers to that name. The cooking of Italy is really the cooking of regions that long antedate the Italian nation, regions that until 1861 were part of sovereign and usually hostile states, sharing few cultural traditions and no common spoken language—it was not until after World War II that Italian began to be the everyday language of a substantial part of the population—and practicing entirely distinct styles of cooking.