AN AVALANCHE OF CHEESE pours into the test kitchen at the Denver headquarters of Leprino Foods, the mozzarella supplier to Pizza Hut, Domino's and Papa John's. First, thin wisps of low-moisture mozzarella, then a diced alternative, followed by an "artisanal" version, cut short and wide. Then come flavored cheeses made with a mozzarella base, as well as provolone, cheddar and Monterey Jack. Cooks bring out a take-and-bake pizza, a New York-style pie and a stuffed crust, fresh from nearly a dozen ovens. Another course features frozen food made with Leprino products, including ham-and-cheddar Hot Pockets, Stouffer's lasagna and Smart Ones...