What I do most often is take a mug of milk, and in a saucepan, I'll take a little milk and heat it up with shredded cacao until it's melted, then pour in the rest of the milk and heat it up again till it's steaming. Then I'll sweeten it with honey and add vanilla or nutmeg/cinnamon/cayenne depending on my mood. It's the best hot cocoa ever.
You can also reduce the milk and blend it in a Vitamix, and you get this super thick foam on top. That's also great to do with Oshi's chocolate butter to make cold chocolate milk.