FX’s “The Bear” was, for many viewers, a first introduction to the deliciously messy Italian beef sandwich. In the show’s first season, Carmy (Jeremy Allen White) is a fine-dining chef who comes home to Chicago to take over the family’s beef stand following his brother’s death. The show, which returns Wednesday for its highly anticipated third season, provided a close-up look at the inner workings of a restaurant whose sole purpose was preparing the meaty, juicy sandwich.