115A North Duke Street, Durham

When Kaffeinate opened near Durham’s Brightleaf Square last fall, it wowed the Instagram set with its black-sesame latte. The seeds adrift in the white foam cap are all the more photogenic because they match the ninety-year-old black-and-white tile floors. (The building was once a Studebaker car dealership.)

Then the shop upstaged itself with the Okinawan Steamer, a comforting, just-a-touch-sweet steamed-milk drink made with purple sweet potatoes. While the drink was not intended to be a permanent menu fixture, its striking pastel hue (#nofilter) has taken it from chalkboard special to being the cafe’s specialty. Few can resist snapping a shot for social media before they sip. It’s also available iced, where its color shines brightly in a Mason jar.

But the Okinawan Steamer is more than Instagram bait. With his father and sister, Kong and Diana Lee, coffee enthusiast Raymond Lee opened Kaffeinate in the former Respite Cafe space on North Duke Street. Born in Queens and raised in Raleigh, the Lee siblings are first-generation Korean Americans. They want their cafe’s menu to draw flavors and influences from their heritage, but without being defined or restricted by it.

Raymond Lee has long had the idea for a sweet potato latte in mind. In Korea, they’re as popular as pumpkin spice lattes are in the U.S.; Seoul-based chain Hollys Coffee serves its signature almond-topped sweet potato latte year-round. Lee wanted a sweet potato latte to be one of his cafe’s signature drinks but wasn’t satisfied with the recipe in time for the opening.

A few months after Kaffeinate opened, Lee’s father brought him some purple Okinawan sweet potatoes that a friend gave him. They were meant as a snack, but their serendipitous arrival revived Lee’s idea.

“It took a while for us to develop a recipe that was both delicious and kept the beautiful color of the sweet potato, but the end result is the Okinawan Steamer,” Lee says.

Lee found the Okinawan sweet potatoes hard to source regularly, so he switched to a locally grown variety of purple sweet potato he could get at the farmers market. (But by then, the name had stuck.)

Lee buys the purple sweet potatoes at the Raleigh Farmers Market, then steams and purees them before mixing them with steamed milk, spiced with a proprietary blend. Maple syrup draws out the tuber’s natural sweetness and balances the starchy, vegetal taste, along with a dusting of cinnamon on top. While the drink is best presented in all its purple majesty as a noncaffeinated steamer, espresso is an add-in option, and the full-bodied, locally sourced coffee tones down the sweetness even further.

You can order the espresso on the side to sample it both ways, but it’s fun to watch the staff add it, too. The espresso shot must be poured high above the foam so as not to muddle the color, and Lee and barista Toni Partin are ace enough leave the purple foam intact.

Though the Okinawan Steamer is a hit among those in the know, some customers are hesitant about drinking something with potato as an ingredient, no matter how alluring its color. But Partin remains confident that doubters will be pleasantly surprised.

“People are always very curious about the taste, but I encourage them to try it, and I’ve yet to have a person bring it back to me or tell me they didn’t like it in the eight months we’ve been open,” she says.