In Italy, radicchio is quite popular. Usually, it is eaten grilled in olive oil, or mixed into dishes such as risotto. In recent years, it has gained popularity in the United States, but is more often eaten raw in salads. This recipe calls for radicchio di Treviso. Firm, round bitter heads of radicchio (radicchio di Verona) can be found in many supermarkets, but you will probably have to shop at a farmers' market to find the elongated radicchio di Treviso, a variety that is prized for its flavor.
Selection: Heading radicchio should have some give. If it is too firm and heavy, with leaves no longer attached to the core, it is probably over mature and won't last long. With all types, select radicchio as you would any salad green, avoiding specimens that show signs of decay such as brown-edged leaves or browning cores.
Storage: Store in a loose plastic bag in the refrigerator crisper. Radicchio keeps a few days longer than most salad greens.
(If you can't find the elongated radicchio, feel free to use whatever you can find in your grocery stores.)
From the cookbook: Fresh From the Farmers' Market by Janet Fletcher