When you bite into a vegan s’more cupcake from the Cupcake Bar, remember it took two weeks to perfect that marshmallow.

One recent morning, owner Anna Branly wielded a miniature torch over a tray of square marshmallows, toasting them to an optimal color of copper. When finished, these egg- and dairy-free sugar bombs will land atop vegan s’mores cupcakes, the bakery’s dessert entry in this month’s Bull City Vegan Challenge.

The Cupcake Bar sells vegan versions every Saturday, but for the challenge, they will be available every day.

The frosting is made with a vegan butter substitute, but Branley says, “The science is in the eggs.” In lieu of ova, Branly uses vinegar and baking soda.

As for marshmallows, traditional versions contain sugar, flavoring and gelatin, which is derived from animal products—the boiled down bones, tendons, ligaments of cows or pigs.

After a fortnight of experimentation and, Branly says, “a lot of steps,” she and her fellow bakers found the right combination of soy protein, cream of tartar, sugar and agar agar, the latter of which thickens the mix that is beaten like a meringue.

“We just kept trying,” Branly says. “I knew it could be done.”

The Bull City Vegan Challenge runs through Feb. 28. Other participating eateries are The Parlour, Hummingbird Bakery, Taberna Tapas, Dos Perros, Parts & Labor, The Refectory Café and Beyu Caffe. The Cupcake Bar is at 101 E. Chapel Hill St., Durham, 919-816-2905, cupcakebarbakery.com.

Info about the challenge is at www.trianglemm.com. —