B&H is a place to try; enjoy the food and be transported back to a 1940s Jewish diner emblematic of life in NYC before the demographics and the cost of living changed dramatically.
It is a kosher, vegetarian restaurant though for those more religious, check for a hashkacha.
The dishes here are truly delicous; I recommend the egg and cheese on challah, the blintzes, the pierogies and, for the adventurous, the whitefish melt.
As a mac and cheese connoisseur, it should be a lot of fun to see the big tray of melted gooey awesomeness open on the counter to fill a bowl for a mac and cheese order.
The food is very inexpensive and the clientele are salt of the earth, compromising workers in the area, local residents, and the cognoscenti of whom you are now a member.