Plac Nowy is a known area for 3 things - meat and sausages at Grill na Kazimierzu, the Polish sandwich zapiekanki at every other vendor in the giant circle of the plaza, and being the area where people go at night for drinks.
Sadly as I was there on a Monday night, there was no nightlife of people at all - irritating because the hostel staff specifically told us to go there for it. I don't think it had anything to do with not being local as we walked the entire area and even asked a bargirl in the one place we found open, who confirmed nothing happens there on Mondays/weekdays.
Still, two out of three is ok.
Grill na Kazimierzu
A little stand in one corner that has loads of bbq options cooking in anticipation of the crowds. The lady running it didn't speak English but there is picture signs for guidance or alternatively point at what you like on the grill. I tried a sausage (simple, standard, satisfying, nothing amazing) and a piece of the local delicacy bbq cheese (which is quite dry and not particularly tasty).
Zapiekanki
This Polish sandwich is what the afterwork crowd, the local youth, and the budget travellers seem to try. It is effectively a very long bread half topped with a plethora of options to resemble a pizza. Various meats, vegetables, cheeses and sauces are added and then baked to be warm and bread crisp. I hadn't researched if any one was particularly better than the others, but they all seemed to look the same. I chose one that had no English on the menu and had other customers there already.
My selection of chicken, cheese, tomato sauce and spring onion was pretty terrible. The bread was crisp but had no intrinsic flavour, the chicken didn't have much flavour either, the cheese was melted but bland. In the end it tasted like bread with tomato sauce and a jumble of flavourless meat/cheese. I ate a few bites and left the rest on a bench top for a friendly hungry soul to have.
Next time I would order from Plac Nowy only on a night when there was more atmosphere (likely Thurs-Sat). Kazimierzu will satisfy the basic sausage cravings. I would be willing to give zapienkaki another try, but I'd have to choose my vendor and toppings much more carefully.