Shake Shack secrets: 10 things customers probably don't know

10 Shake Shack facts every burger fan should know. (iStock)

When you bite into a Shake Shack burger, you probably think about the melty American cheese, the patty's super-crispy griddled crunch, and how everything should be served on a pillowy Martin's potato roll.

With 129 locations internationally (and counting), it's hard to imagine the restaurant's humble beginnings 16 years ago as one small hot dog cart in Madison Square Park. The stories behind the "fine-casual" chain's now-famous dishes are chronicled in CEO Randy Garutti and culinary director Mark Rosati's cookbook, "Shake Shack: Recipes and Stories" — with an eye-opening introduction from Union Square Hospitality Group restaurateur Danny Meyer. It's a fascinating read whether you're hungry for recipes or insider trivia about the cutthroat New York restaurant world.

We've rounded up 10 of the most surprising facts we learned:

1. It could have been named Dog Run.

On the original menu, some surprising names were tossed around: Frostee Shake, Madison Mixer, Parking Lot, Custard’s First Stand, Dog Run and Custard Park. The Shake Shack menu is pretty streamlined now, but they once thought about including a tuna burger and two or three varieties of doughnuts.

2. The burger taste-testing was super intense.

Bon Appétit's food director Carla Lalli Music was Shake Shack's first-ever general manager from 2004 to 2005. She would eat one bite of a ShackBurger and one bite of chocolate custard for quality control every day, and she wishes that the root beer float-flavored custard caught on. Long before the restaurant served breakfast at JFK Airport, they attempted to launch it at the original Madison Square Park shop, but it didn't stick. In the book, she recalls reporting ratios of meat to fat in the patties daily to meat purveyor Pat LaFrieda. "We would get on the phone to Pat and report our findings; he’d retool on his end, even sending a new batch that same day, and before too long we were at a place where the burgers hit that sweet spot 999 times out of 1,000."

3. They lost money for the first three years.

“We promised to donate 100 percent of our profits to the Park [Madison Square], which was sort of easy since we lost money in years one and two," Meyer reveals. "I’ve said we made $7,500 in year three. Actually, we didn’t. I was just so embarrassed that we’d lost money for three years, we chose to make a bigger contribution.”

4. The ShackSauce recipe is secret...ish.

Even though they won't give up the official secret recipe, they give a "close enough" version in the book. Combine ½ cup Hellman’s mayonnaise, 1 Tbsp. Dijon mustard, ¾ tsp. Heinz ketchup, ¼ tsp. kosher dill pickling brine, and a pinch of cayenne pepper. Add it to a classic smash burger, and you're in business.

5. They spent $1 million testing fresh-cut fries.

Pete Wells’ 2012 New York Times review questioned why Shake Shack used frozen fries. The team was so shook that they spent $1 million experimenting with different fresh-cut fry styles. After they converted the whole company to fresh fries, fans complained that they missed the crinkles and their potato-cutting devices started falling off the walls from overuse, so they brought back the frozen stuff.

6. Spicy ShackSauce exists.

When developing the Chick'n Shack, they thought about making ground chicken burgers or grilled chicken sandwiches, but ultimately Meyer wanted fried chicken — with ShackSauce. They developed a spicy ShackSauce, but it never made it into restaurants because they worried people wouldn't be able to tell the two sauces apart. Instead, they went with a buttermilk ranch for the fried-chicken sandwich that took two years to perfect.

7. DIY cheese sauce is so easy.

Their base for a "close enough" version of their signature cheese sauce is sautéed onions and jalapeños steeped in a combination of cream, white wine vinegar, and white wine for 30 minutes to infuse flavor. Instead of melting cheese into it on the stove, you strain the cream mixture and pour it over equal parts grated American and cheddar cheese to melt it all together for a smoother sauce.

8. There's an Official "Shake Ratio."

If you get a hankering for a shake in the middle of the night, just blend together 1½ cups custard (or your favorite premium ice cream, they say) and ½ cup milk. If you want it flavored, add 2 Tbsp. of your favorite sauce and ⅓ cup milk instead of plain ol' milk.

9. A cult-favorite, off-menu burger has peanut butter.

The peanut butter bacon burger has only been served twice in the restaurant's history, but you can always order a bacon hamburger and ask for a side of peanut butter sauce if you really want to try it.

10. One day, chicken bites may be a reality.

There's a recipe for chicken bites — aka nugget-sized versions of the sandwich — in the cookbook, but they don't exist at restaurants … yet. Danny Meyer, if you're reading this, we'd like to dip some of those little guys in ranch ASAP.

Reprinted from "Shake Shack: Recipes and Stories." Copyright © 2017 by Shake Shack Enterprises, LLC. Principal photographs copyright © 2017 by Christopher Hirsheimer. Published by Clarkson Potter/Publishers, an imprint of Penguin Random House, LLC.