Best-Ever Hot Cocoa Mix

"Why this recipe works:We wanted a recipe for hot cocoa that was creamy, rich, and big on chocolate flavor. Nonfat dry milk lent our Hot Cocoa Mix recipe a sweet dairy flavor, especially when we reconstituted the mix with hot milk instead of hot water. Confectioners’ sugar worked best in our recipe because it dissolved quickly, and cornstarch helped thicken the hot cocoa. And for complex chocolate flavor and a soft, creamy texture, we used a combination of white chocolate and cocoa powder...."