Patrons who wander on weekends through the Artists and Fleas market in Williamsburg know the founders of Mast Brothers Chocolate as much for their red, Amish-style beards as for the handmade bars they sell wrapped in floral- and paisley-printed papers.

Unlike the many chocolatiers who use couverture — discs of premade chocolate that can be remelted for confections and bars — Rick and Michael Mast count themselves among a small cadre of artisans who make their chocolate from cocoa bean to bar. “You have a lot more control over the quality of the process — and so much of the flavor development comes from the roast of the bean,” Rick, 31, said of the batches of bars and custom-made bonbons they have been making out of Michael’s Greenpoint apartment.

“Plus,” Michael, 28, added, “it’s a challenge.”

Mast Brothers Chocolate, in business since last year, also sells its $7, 3 oz. bars at Marlow & Sons, Spuyten Duyvil Grocery, and Urban Rustic, all in Brooklyn. But come fall, the brothers — having pooled their savings and maxed out their credit cards — will open their own chocolate factory and store at the corner of Wyeth and Berry streets in Williamsburg. (The address of their new shop is the inspiration for their new white chocolate and cranberry bar, not surprisingly called the Wyeth Chocolate and Berry Bar.) “There are no outside investors and no trust funds,” Rick said of their new store. “I feel like I have to get that out there because everyone in this neighborhood is so cynical.”

For the time being, though, they are making due with an apartment-size kitchen, where the interior thermostat — regulated by an infrared thermometer — is always set for the chocolate’s comfort level, not that of the human inhabitants or visitors. The scent of the chocolate is worth the occasional chill, Michael said, noting: “It makes the apartment smell nice.”

They employ classic French confectionary techniques Rick gleaned while apprenticing under the legendary chocolatier Jacques Torres. Adhering to old-fashioned culinary traditions, the brothers do everything by hand: folding parchment into little cornets, or cones, and manually smacking their chocolate molds on a table to get rid of any air bubbles. “You can buy prefab cornets or mechanical vibrating tables designed just for this purpose, but to me it takes away from the authenticity,” Rick explained.

The brothers are lanky, despite a steady diet that includes at least two cups of hot cocoa and any misshapen confections that these beatnik epicureans do not consider good enough for their customers. As Rick put it: “We’re trying to teach people enough so they can enjoy the best.”

For them, that means chocolate derived from “fair trade” cacao beans from Venezuela, Dominican Republic, and Ecuador. Liberal handfuls of Cape Cod cranberries, almonds brushed with Celtic sea salt and extra virgin olive oil, and walnuts sautéed in maple syrup imported from Quebec are among the ingredients in their seven types of chocolate bars, whose base is between 40% and 81% cacao.

On a recent morning, the brothers set to work on two trays of custom-ordered white chocolate bonbons infused with Jamaican chili pepper ganache. Rick selected a fresh tray and, using simple brushstrokes and red colored cocoa butter, painted a delicate contemporary design on each mold. Then the molten chocolate was poured in. Making the chocolate base used in each shell requires a four- to five-day process of mixing, heating, and cooling.

After the Caribbean-spiced chocolate-cream ganache was injected and the bonbons chilled, Rick hunched over the finished product to examine his work. “You look at the design and how it influences the expectation of flavor,” he said of the abstract scarlet brushstrokes indicating cinnamon chili. “Is it going to enhance the experience? You eat with your eyes first.”