Hot chocolate is a rich enterprise. Although you can use milk, bitter/semi-sweet chocolate begs {heavy} cream, and then what you have on your hand is the opinionated view of your expensive chocolate versus how you're going to explain to anyone else why it's ok to drink ganache. We're talking seriously supple, silky and smooth, but at the cost of your arteries, and for me I would rather slather a wide mug of hot cocoa with whipped cream to amend the whole milk.
The most famous hot chocolate of my generation is created by the slightly wicked, darkly humoured Maury Rubin, pastry chef/ baker/ owner of City Bakery in NYC and Los Angeles. He is smart enough to serve it in a thimble-sized portion for reasonable, informed persons, and has a larger portion for those unawares of what lies within. Not only are there no words to describe what Maury's hot chocolate is like, even if I had any, they would disappear under the weight of this brutally rich concoction. Yes, I like it, but I have been known to share the shot size with more than one other person. No joke, yo.
I have a few tricks should you like to take hot cocoa on as a end of year meal amending or replacing project. Years of making beverages, ice cream, cakes, frostings, ganache, truffles and more with cocoa and chocolate have given me insight to a number of cocoa and chocolate personality quirks.
Chocolate and cocoa have little to no flavor when they are cold or frozen. Cocoa's chocolatey-ness can only be achieved if added to warm or hot liquid. If cocoa is added to cold or cool liquid and then heated up, the cocoa will float to the bottom of the pot and burn on the bottom. This scorching will destroy the flavor of the dairy.
Every cocoa is not only different in terms of its manufacturing process, but not one of them is ground to the same particle size. You may think you don't care about such minute details, but 4 teaspoons of one cocoa is not 4 teaspoons of another. If you are making a large batch of hot cocoa, as I have begun to at work in preparation of all the ice skaters in Justin Herman Plaza, measure cocoa by weight. If you have a scale that can be adjusted to grams, do so. Good quality cocoa is strong and a smidge goes a long way.
If you are making hot chocolate, it is best to chop chocolate fine and place in a large, wide mouthed bowl. Heat cream/milk until just boiling and pour over chocolate. Let sit a few minutes and then whisk in tight concentric circles, from the interior, out. Although you can make hot chocolate with milk, you will find that cream or half & half will emulsify with the solid chocolate better. It's never a good idea to cook chocolate right in a saucepan because it burns so easily, but if you want to heat up your mixture again or more, place bowl over a pot of boiling water and whisk until desired consistency. Or a microwave can be you fast friend.
I'm one of those odd ducks who likes a big mug of hot cocoa to be unsweetened or barely sweet. But if you like yours a little sweeter try using brown or raw sugar. The caramel-ly flavor of these sugars backs up the chocolate taste nicely. And lastly, a tiny pinch of kosher salt is a nice finesse.
Because hot cocoa and hot chocolate are made up of just two or three ingredients, making sure your dairy is the best quality is a good idea. Ultra-pasteurized milk and cream can sometimes have stabilizers that read on the tongue as bitter and can interfere with your hot cocoa purr.
This is how I make hot cocoa:
I pour about 2 cups of whole milk into a non-reactive saucepan, sprinkle about a teaspoon of sugar in, and then turn flame to low or medium. When milk is hot to the touch I sprinkle in cocoa one teaspoon at a time, whisking constantly, until it tastes right. I continue to whisk for about 5 minutes, but I try not to let it boil.