Didn't grandmothers used to sell "banks" in front of subway stations a long time ago?

I don't remember exactly which station it was when I was a kid,
but anyway, I remember grandmothers selling roasted "banks" (sweet potatoes/snacks) near the exits of Line 2,
and I remember them being really delicious.
I feel like there used to be many people selling those kinds of things in a few slightly busy stations,
but I haven't seen them at all for some time now.
Has anyone else tried them?