It’s a marriage made in gourmet burger heaven: a five-ounce, all-beef patty dripping with cheddar cheese and fried onions – served between a glazed doughnut.

Specialty burger restaurant PYT in Philadelphia says its limited edition Donut Cheesesteak Burger is a novelty take on the city’s signature classic, the Philly cheesesteak sandwich.

“It definitely has sweet and savoury elements to it,” executive chef Kim Malcolm said. “The donut is sweet, but not overpoweringly so, (and) the real beefy flavour cuts through.”

On the menu as PYT’s “burger of the week”, the $US15 ($A16) creation is finding a following, amid social media buzz.

It faces stiff competition from the innocently named “bruleed French toast” at Cheesecake Factory, a national restaurant chain, which packs a whopping 2780 calories.

The Center for Science in the Public Interest declared the dish – custard-soaked bread topped with powdered sugar, served with bacon and maple syrup – America’s most caloric as it announced its Xtreme Eating Awards for 2014.

For the title of “single unhealthiest meal”, the advocacy group cited another big chain, Red Robin, for its “monster” combo of peppercorn burger, “bottomless steak fries” and salted caramel milkshake – about 3540 calories altogether.

“To dispose of those calories, the average person would need to walk briskly for a full 12 hours,” the centre said.

Last year, burgerdom reached for the heavens when Chicago restaurant Kuma’s Corner introduced the Ghost, a 10-ouncer topped with red wine and a communion wafer.

Popular among many patrons, it nevertheless rattled some Catholic regulars with its allusion to the blood and body of Jesus Christ, the Chicago Tribune newspaper reported.