This stretch of rolling dairy country has long been Milton Hershey's turf, where he found success making chocolate more than a century ago and earned a name synonymous with chocolate in America. But M&M-making rival Mars has crept up on Hershey's dominance of U.S. chocolate buyers. And now, Mars has delivered a chocolate-coated slap in the face, setting up shop in south-central Pennsylvania, just 10 miles from Hershey's flagship factory on Chocolate Avenue. While Mars makes its mark with the $70million “Dove Chocolate Center of Excellence,” Hershey has struggled to cut costs by closing U.S. plants and blending cocoa butter substitutes into some of its chocolate candy — a step that has riled candy enthusiasts who say it dulls the flavor and feel of pure chocolate. At the unveiling of its newly expanded Dove factory in late September, Mars Snackfood U.S. president Todd Lachman said — without naming Hershey — that cost-cutting competitors are “tricking” consumers with substitutes and outsourcing American jobs. “The consumer is our compass, and we will always deliver 100 percent real, authentic chocolate products that have been manufactured here in the United States,” Lachman said. Mars also has pivoted its PR messages to chide its rival: Its premium brand Dove is “Made in the USA” and Mars can be trusted “to provide pure, rich chocolate,” it says. And Mars is making its case just as it's leapfrogging Hershey as America's largest can ...