Shake Shack expands hotly anticipated chicken sandwich

We can tell you where our ingredients come from: Shake Shack CEO
We can tell you where our ingredients come from: Shake Shack CEO

Shake Shack is going beyond the beef.

The restaurant chain plans to launch its first ever chicken sandwich, the Chick'n Shack, nationwide on Thursday at participating locations.

Investors and customers have closely watched the sandwich since reports surfaced last spring that Shake Shack filed a trademark application for "Chicken Shack." Shake Shack began testing its first chicken sandwich at its Brooklyn locations during the summer.

Read More Shake Shack celebrates chicken sandwich by ringing NYSE bell

In Brooklyn, the item has grown to a top-five seller, Shake Shack CEO Randy Garutti said at the ICR Conference on Tuesday.

Chickn' Shack burger at Shake Shack.
Photo: Liz Clayman

In the tests, adding more chicken to the menu helped Shake Shack diversify its market basket, one-third of which currently consists of beef, and eliminate the "veto vote" from customers who do not want to eat beef, Garutti said.

The $6.29 Chick'n Shack will be available at all domestic locations, except the NYC Theater District restaurant, stadiums and JFK Airport. The Theater District location will start serving it shortly after the nationwide launch.