Eater has identified two restaurants in the neighborhood with “secret”, off the menu burgers. The first is at Gramercy Tavern (42 East 20th Street), which has an off-the-menu cheeseburger (cheddar cheese, lettuce, raw onions, and pickled onions) at lunch. They butcher and grind the beef at the restaurant according to Eater. The second is Hillstone (378 Park Avenue South at 27th Street), where they have an off-the-menu fresh ground Hickory Burger (Cheddar, Canadian Bacon, BBQ sauce). We love the Hillstone Veggie Burger, but have never had the Hickory Burger.
If you must leave the neighborhood, you can check out 3 more secret burgers at http://ny.eater.com/archives/2013/03/secret_burgers.php.
Know of other secret off menu items in the neighborhood, email info@MadParknews.com.