Mac & Cheese Restaurant
...or MacBar in Soho.
...or Supermac (which is temporarily closed while they relocate to a bigger space)
Personally, I liked MacBar the best (the Reuben Mac and Mac Quack are both great) but S'Mac is pretty good too.
Granted, eating at any of the above more than once a month is pretty much a guarantee of arteriosclerosis...
348 7th Ave, New York, NY 10001
54 Prince St, New York, NY 10012