Chocolate made from 100 percent white beans is extremely expensive. (When roasted the beans turn brown and they are unrelated to “white chocolate.”)

Cacao is thought to have originated in the rain forests at the source of the Amazon and Orinoco Rivers and then gradually dispersed northward. What surprised Dr. Meinhardt the most about Mr. Pearson’s cacao was that it was growing at an altitude above 3,500 feet, while cacao rarely grows above 2,000 feet.

In the canyon, 186 farmers are growing pure Nacional. The beans are transported to a town several hours away, where they are dried, fermented and roasted, then sent to Lima and shipped to Switzerland. The chocolate is processed there by a company recommended by Mr. Zeigler, which Mr. Pearson did not want to name. The beans are made into what they call Fortunato No. 4, a 68-percent bittersweet couverture, a high-cocoa butter chocolate that’s easy to use.

They have 15 tons of it in slabs. A company in Switzerland and one each in Germany, Canada and the United States (Moonstruck Chocolatier, of Portland, Ore.) are making candies and bars with the chocolate.

At Moonstruck, the exclusive American retailer for the chocolate, Julian Rose, the chocolatier, is coating pure Nacional beans with pure Nacional chocolate. These will be introduced this weekend at the Fancy Food Show in San Francisco, and are sold as Fortunato Tumbled Beans at moonstruckchocolate.com ($12 for 3.5 ounces; bars of Peruvian Fortunato are $12 for 2 ounces). Mr. Rose said the flavor of this chocolate is so refined that it does not need vanilla, commonly added to chocolate, to round it out.

At the Institute of Culinary Education in New York, Michelle Tampakis, the director of advanced pastry studies, said the chocolate was extremely smooth when melted, with a full-bodied, nutty flavor that was not bitter.

Mr. Zeigler, who visited the canyon with Mr. Pearson last year, said he had a “Jurassic Park feeling” about the experience. “And the discovery of the white beans tops the whole thing,” he said. “I have no doubt this chocolate will be up there with the very best in the world.”