Durian has become so popular in China that it's now the key ingredient to Pizza Hut's best-selling pizza in the country.Carlina Teteris/Getty Images and Costfoto/NurPhoto via Getty ImagesDurian pizza is now Pizza Hut's hottest pie in China, with Yum reporting 30 million sold this year.Yum China's CEO, Joey Wat, said on Monday the dish is now Pizza Hut's "No.