The line outside B. Doughnut is already starting to form at eight o’clock Saturday morning, even though it won’t open for another hour. Some of the customers sit in chairs outside the shop on Loudoun Street in downtown Leesburg, reading a book or swiping at their phones to pass the time.

By 9 a.m., when the door opens, the line has grown to more than 40 people. Greeted by the mingled aromas of roasted coffee and fried dough, the customers begin placing orders for doughnuts with their favorite fillings and toppings — vanilla bean, lemon curd, cinnamon sugar.

Before long, the most popular varieties are sold out. Although each customer is limited to a dozen doughnuts on weekends, the shop usually closes in less than three hours because all 1,500 doughnuts have been sold.

On a frosty Saturday morning last month, several customers explained why they were waiting outside in the 25-degree chill to buy doughnuts that ranged in price from $2.50 to $3.75 each.

“They’re delicious,” said Ben Atkins of Bristow. “They’re light enough to where you can actually enjoy multiple of them.

B. Doughnut’s owners Pin and Brian Chanthapanya say their yeast doughnuts are handmade with fresh ingredients. (Jim Barnes/For The Washington Post)

“They’re not super sweet . . . just perfect balance,” he added. “The dough’s nice and light and just chewy enough — much different than your traditional cake doughnuts.”

Ashburn resident Faizan Khan said the doughnuts are “awesome.”

“My daughters love them,” he said. “So that’s why I’m standing out in the cold, suffering.”

Jecholia Gallagher of Hamilton said she had brought her daughter Chloe for a special treat after a baby ballet class.

“She likes the pink one with sprinkles,” Gallagher said. “Sprinkles are very important for a 2-year-old.”

Brian Chanthapanya, who owns B. Doughnut with his wife, Pin, said the doughnuts are handmade with fresh ingredients.

“Our doughnuts are yeast doughnuts — more fluffy and airy in the middle,” Pin Chanthapanya said.

Brian said he came up with the doughnut recipe “just messing around at home.” Although he had been working in the information technology field, he had long wanted to run his own company.

The couple started the business a few years ago in the garage of their home in Sterling, making deliveries on weekends. They opened the original B. Doughnut shop — the “B” stands for Brian — in Baltimore, where several publications hailed it as serving one of the city’s best doughnuts.

Despite the shop’s success, the couple closed it after a year and a half because they found the commute from their home in Loudoun to be too difficult. They settled on downtown Leesburg for their new location because they saw promise in the town’s growing mix of dining and entertainment establishments.

“We were hoping that someday it would be kind of like Georgetown, a scaled-down version,” Brian said. “We wanted to help with the growth of downtown, too. I’ve seen traffic pick up a little just because we’ve been here.”

Last year, buzz began to build that B. Doughnut would be opening in a small storefront across from the town parking garage. Brian said the business received a boost in publicity from social media, particularly “Real Housewives of Loudoun County,” a popular Facebook group that has almost 17,000 members. When the shop opened Dec. 1, the customers were waiting.

“Our first two weeks, people were waiting in line almost two hours before we opened,” Brian said.

The shop is open only four hours Thursdays and Fridays and three hours Saturdays and Sundays. It closes early when the doughnuts sell out. Nevertheless, Brian expressed confidence that the business is sustainable.

“We tested [the business model] in Baltimore,” he said. “We’re constantly improving the process to try to make it easier on us, because it’s a lot of work.”

Making yeast doughnuts is a time-consuming process, he explained.

Brian typically arrives at the shop at 11 p.m. and works through the night, mixing the dough, rolling it by hand, letting it rise, pushing it down and letting it rise again. He starts frying the doughnuts about 5 a.m., “so we can have a good supply for the morning rush,” he said.

Pin, who gave birth to the couple’s third child in November, usually arrives around 6 a.m. Not long afterward, the line starts to form outside.