I went behind the scenes at a world-famous doughnut shop. Take a look inside.

Despite it being a dreary day, customers were already lined up inside to grab their breakfast.

The Holy Donut was dreamed up by single mother Leigh Kellis in her apartment kitchen. After trying multiple different recipes, including one from the iconic cookbook "Joy of Cooking," Kellis came up with her own recipe for a doughnut using riced Maine potatoes.

The result was a doughnut that was heartier and heavier and didn't dry out as fast as a typical doughnut.

The business has since grown into a local institution with five locations and now has even bigger dreams, largely thanks to Buckwalter.

"I think a big part of our story is it's a wonderful American dream story. The family coming together and just figuring it out," he said. "Also, within a community that has — I don't know that it doesn't exist outside Portland — but has a rising tides mentality. Everybody is willing to help everybody."

The Holy Donut, which employs over 120 people, has locations in Brunswick, Scarborough, Arundel, and two in Portland.

The location in Arundel is its commissary location, where 60% of The Holy Donut's products are made, including all of its gluten-free items.

Buckwalter told BI that the company's location in the heart of the Old Port neighborhood, right across from the pier, has boosted business and brand awareness.

"Commercial Street is one of three places I've always kept my eye on; if any of these three pop up as available, that's where we want to be," Buckwalter said, adding that the street has become the "nexus of the Old Port."

Blueberry season in Maine typically lasts from late July until early September, and blueberry festivals are held across the state in the late summer.

Buckwalter said The Holy Donut leans into seasonal, limited-time-only flavors, from its summertime blueberry flavors to apple cinnamon sugar doughnuts in the fall. It's an exciting time for customers to embrace the season and get their favorite flavors that they wait all year for.

In the freezer, I saw how The Holy Donut uses real Maine blueberries in its famous blueberry doughnuts.

Buckwalter said that using local ingredients, like the Maine potatoes it uses in nearly all of its doughnuts, has become a huge part of creating The Holy Donut's brand as it positions itself for nationwide shipping.

"This is what we've always done, a handmade product. So it was like, how is that going to shift the image of our brand? And really, market research showed that the fact that the doughnuts are made by hand is not in the top five reasons," Buckwalter said.

"That it's fresh, that we lean into local, that we are family-owned, that we're kind and thoughtful in the community, all those things are far more important than that," he continued. "This is a from-scratch product every single day."

Buckwalter said that while the company has made steps to automate some processes over the years, the doughnuts are still cut and shaped by hand — something he believes is integral, though not the most important aspect, to the company's brand.

"[The number of] personal injuries was crazy in the early years. We were breaking people. Because our absolute killers, like Campbell, he could hand-cut, when he's in the groove, 500 doughnuts a minute, like boom, boom, boom, it's a blur," he said.

"But that comes at the expense of elbows and wrists. So, first thing first, let's stop breaking our people. And then secondarily, for the scaleless things, we always knew we'd have to automate," he added.

Buckwalter said that across its locations, they probably make around 6 or 7 million doughnuts each year. Demand is particularly high during the summer when tourism in Maine is at its peak. The stores each sell different quantities depending on their location.

"Our Arundel one is a very small, tiny retail," he said, adding, "Purchasing that was all about the commissary and its proximity to the interstate."

Each doughnut is priced individually and ranges from $4.25 to $5.25. You can also order a half-dozen assorted donuts for $22 or a full dozen for $44.

The price may seem higher than your average doughnut, but thanks to the potatoes included in the recipe, I thought these doughnuts were heartier than other doughnuts I've had.

"We are going to own the doughnut shipping space nationwide and we are going to be known as a very well-managed and scaled family company that now has a nationwide brand," Buckwalter said of his goals for The Holy Donut in the next five years.

He said that while the company has been in talks with massive distribution giants like Goldbelly, his team is starting off on a smaller scale by creating an online ordering system and shipping its own products across the country — an option that will be rolling out soon.

"We've perfected freezing our product, so that's been a complete game changer for us," Buckwalter said. "Now, these stores can really best be served as profitable marketing arms that drive traffic to our shipping, and drive traffic to our soon-to-be nationwide retail. We have a lot of work to do, but within a couple of years, that's a very real opportunity for us."