KANSAS CITY, MO. — New formulations of hamburgers are joining menus at quick-service restaurants.

White Castle is bringing back its 1921 slider, but with a spicy twist. The slider features ghost pepper cheese, as well as caramelized grilled onion, lettuce and two pickles.

“We’re always looking for ways to give Cravers what they want, and they’ve been vocal in letting us know they were looking forward to the return of the 1921 slider with ghost pepper cheese,” said Jamie Richardson, vice president at White Castle. “This slider embraces the spice of the cheese while maintaining the flavors and deliciousness that Cravers anticipate every visit.”

Freddy’s Frozen Custard & Steakburgers is going big with its new steakburger stacker, which features three steakburger patties, American and white cheddar cheese, lettuce, tomato pickles and Freddy’s fry sauce.

The Habit Burger Grill, a California-based chain, is also giving its burgers a spicy update, with the return of the limited-edition jalapeño char burger. The burger features a chargrilled patty topped with American cheese, a spicy jalapeño jam, the California-based chain’s jalapeño mustard ranch, lettuce, tomato and pickled jalapeños, all served on a toasted brioche bun.

“We’re always looking to innovate, to bring more craft, to showcase our passion for the perfect char burger — and we think we’ve found it with the updated jalapeño char,” said Jack Hinchliffe, global chief marketing officer at The Habit Burger Grill. “We’ve added several different notes of jalapeño with our delectable jam, creamy house-made ranch and pickled jalapeños — which elevates this burger in every sense — you can taste the craft and care that goes into each bite.”

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