Shake Shack, a popular chain that hasn’t made it to the northwest U.S., builds its burger with all-natural Angus beef, a “Chicago-style” potato bun, the Shack's sauce, which is made up of mayo, dijon mustard and dill pickle brine.
“The final product looks nearly identical to Shack's beloved burger, though the ingredients are slightly different,” wrote Delish.com's Rheanna O’Neil Bellomo, who simply called it a “Shake Shack copycat.”
When the Seattle Times checked in with Costco Corporate about Seattle as a test market, it wouldn’t confirm the cheeseburger. But a reporter found one for sale at the Costco location in SoDo, costing a modest $4.99 and not-so-modest 1,140 calories.
According to Eater, the burger is in a localized testing phase.