Walk into Sandwich Planet, 9th Avenue in Hell’s Kitchen South, and ask for the H23, or “Stewart” sandwich. It is indeed named after Stewart Smith who describes its origin :

I was a fan of their H19 and one day at O R G we placed some Sandwich Planet lunch orders. I decided I wanted my H19 with avocado on it. “A bold move,” stated Prem. During lunch everyone began referring to my sandwich as “The Stewart.”

The next time we ordered from Sandwich Planet I made sure to place the call, asking the operator for a “Stewart Sandwich.” Their shop is known for having several celebrity-namesake sandwiches, but none of these happened to be Stewarts. When the operator asked me to repeat myself I replied, “You know—the Stewart Sandwich; that’s an H19 with avocado.” Apparently they found this humorous and they added it to their menu.