Shake Shack (NYSE: SHAK) is testing out a brand new kind of sandwich titled "The ChickenShack." The sandwich, which consists of a piece of antibiotic-free fried chicken, lettuce, pickles and buttermilk herb mayo, is available only for a limited time at Brooklyn Shake Shack locations. The sandwich currently retails for $6.29. According to Business Insider, this new menu item comes in direct competition with Chik-fil-a, the most popular chicken fast food chain in the United States. For more business and financial news, click here.