Just when you thought you knew the best of Northern Italy, along comes Lynne RossettoKasper to introduce you to Emilia-Romagna, a fertile wedge between Milan, Venice, and Florence, as gastronomically important as any land in the world. The lush homeland of balsamic vinegar, Prosciutto di Parma, tortellini, and Parmigiano-Reggiano cheese, this is a region venerated by Italy's food cognoscenti. Ask an Italian where to take only one meal in Italy,...