There’s a little corner of sandwich heaven hiding in plain sight in Lisle, Illinois, where Schmaltz Delicatessen has been quietly perfecting the art of the Reuben while flashier eateries come and go.

Nestled in the unassuming suburb of Lisle, there exists a culinary treasure that locals have been trying to keep secret for years – Schmaltz Delicatessen, home to what might just be the most ...