Bruschetta with Mozzarella, Treviso and Balsamic Vinegar

Treviso is a type of radicchio, or red chicory. It has a deep burgundy colour and, unlike the more common round radicchio di Verona, long, slender leaves. You could use round radicchio or white chicory for this recipe, but if you can hunt it out Treviso really is a find. It is very bitter, which is why I always bake it with a little sugar, but you can omit this if you prefer.

Another variation of this recipe, perhaps for a warm day, is to leave everything uncooked except for