I'm not even sure what it is to be honest. Some kind of potato turnover thing?
I've made them before. Potato filling with spices with a dough shell baked in the oven. Simple but delicious. Potatoes were cheap in the old days, so knishes could be made and you could feed a ton of people. As time went by they added all kinds of stuff to them eg. goat cheese etc. The ones you get in NYC area a real plain; in Florida they have hundreds of different types to choose from.
To be frank, I have no clue. My knowledge of jersey is little beyond the meadowlands and the turnpike. But I used to date a girl from jersey and I went there with her family and remembered it being good. Trying to get Paulie a legit knish without making the trek to Yonah Schimmels.
If you send him there he can go to Russ & Daughters and Katz at the same time - a road trip worth the schlep