Whisk together malted milk powder, sugar and cornstarch in a medium size saucepan. Whisk in 1/2 cup half-and-half until mixture is smooth. Add remaining half-and-half and cook over medium heat, whisking constantly, until mixture thickens and begins to boil, 2 to 3 minutes.
Remove pan from heat and whisk in chocolate, until smooth. Whisk in vanilla. Spoon pudding into 4 dessert dishes. Serve warm, sprinkling each dish with some crushed malt candies. Or, if serving cold, scrape pudding into a large bowl, press a piece of plastic wrap onto pudding surface, and refrigerate for up to 1 day. Just before serving, divide pudding among 4 dessert dishes and sprinkle crushed malt candies on top.