What is a knish? Besides being fun to say, it's also steamy and delicious.
It's a pillowy potato creation (sometimes with vegetables inside), hot and wrapped in foil. People sell them on street carts in Manhattan ($3 is a bit steep but I say, well worth the investment, especially if you split it with a willing party).
Apparently knish bakeries exist. This particular knishery (it even warrants its own Wikipedia entry) was but a hop and a skip away from Katz's Delicatessan.
Mmm pastrami followed by potato heaven.