When the bakers at Sydney’s Bourke Street Bakery wanted to create a better chocolate cookie—something with deeper, more complex flavor than your basic baked good—their search for a solution led them to Iran. Our attempt to replicate it led us to the microwave.

“A great dessert should be balanced,” says Paul Allam, who founded the bakery with David McGuinness in the city’s Surry Hills neighborhood in 2004. “David and I had played around with lots of different recipes before we opened the doors.”

The chocolate-sour cherry cookie they settled on is now a menu mainstay. It’s one of the items they make sure to serve all year. “Or there’d be riots,” the pair write in their cookbook, “All Things Sweet.” In fact, the cookie was so popular, it’s one of the recipes Allam brought when he opened the bakery’s first U.S. shop in New York in 2019.

It’s the cherries that set the cookies apart. The tartness of sour cherries—a close relative of sweet cherries but, as the name implies, with a bold acidic flavor—creates a bright counterpoint to intensely rich, dark chocolate. The result is a sophisticated riff on a classic flavor pairing.

Unfortunately, finding dried sour cherries isn’t always easy. “Using off-the-beaten-track ingredients is part of the allure,” Allam says. For Bourke Street, getting ahold of sour cherries was a matter of “looking in the right places,” he adds. “We used to source them from Iran.”

Back at Milk Street, we knew tracking down dried sour cherries from Iran wasn’t an option. So we wanted a way to capture their distinctive tangy flavor using more conventional and accessible ingredients. We tried the dried cherries available at most U.S. grocery stores but found them far too sweet.

Eventually, we landed on our approach: Find a way to make sweet dried cherries taste tart. Soaking them in a bit of balsamic vinegar—the fruitiness of which best complemented the flavor of the cherries—did the trick, except the process was tediously slow.

But we knew heating dried fruit helps it absorb liquid more quickly. With a bit of experimenting, we found that microwaving the dried cherries with the vinegar for about a minute quickly plumped them, infusing them with deep, tangy flavor.

Beyond that, it was a simple matter to adapt the Bourke Street recipe. Two varieties of chocolate—chopped bittersweet and cocoa powder—helped create a cookie dough that baked up with a crisp exterior and a dense, fudgy interior. The result is a not-too-sweet treat that’s still rich.