What is a knish? Anything you want it to be, really. It can be baked like a turnover or fried; it can be square or round; and it can be filled with almost anything you want. In New York, though, a knish is usually filled with meat, cheese, or the classic mashed potato. Like other stereotypically New York foods it was brought to the city by Jewish immigrants. The first knishes in New York were sold in Coney Island around the turn of the century by Rabbi Yonah Schimmel, an immigrant from Romania; the little delicacies proved so popular that in 1910 he was able to open a larger knish bakery, the first in New York.