Penne with Radicchio

Radicchio adds a refreshing, slightly bitter flavor to salads. When it is cooked, it loses some of its bitterness and makes a rich, luscious sauce. The Veneto region of Italy is known for the many varieties of radicchio grown there. The one from Treviso is the radicchio most often used in cooking. It is elongated and shaped a little like Romaine lettuce. The most prized is the one available in late fall called tardivo. It is distinguished by how the tops of its leaves curl in toward