I've experimented a bunch with hot chocolate over the years. There's a spectrum from intense chocolate flavor to high richness, and you need to find the sweet spot. So to speak. Tastes will vary.
The most intense hot chocolates I've had are dairy-free, and are closer to the way cocoa was originally drunk. It sounds like a ripoff ... just chocolate and water. But the chocolate intensity is bonkers. I find it a bit too much, for anything more than a demitasse-sized chocolate dessert. But it's worth trying. I use it as a starting point, and add a bit of whole milk to mellow it out. But I generally like the water / milk blend more than pure milk.
If you prefer richness to chocolate intensity, you can go all the way in the other direction and use ganache. This is a handy formula for restaurants, because the ganache is basically an instant hot cocoa mix. Just stir it into hot milk or hot water.
Overall I prefer bittersweet chocolate to cocoa powder. Not because it's inherently better, but because in practice it's better. Very few companies make cocoa powder that's as good or as interesting as their chocolates. With a handful of exceptions, it's a byproduct. There are some signs that this is changing. For the time being I use a blend of both. Chocolate for the interesting flavors, cocoa for added intensity with less added fat.
Here's a version I've enjoyed:
360g / 1-1/2 cups water
60g / 1/3 cup sugar
120g / 4-1/4 oz Bittersweet chocolate
24g /1/4 cup dutch cocoa
1g / 1/8 tsp salt
240g / 1 cup whole milk
-Heat sugar in a saucepan.
-boil the water separately
-when sugar starts to caramelize, stir vigorously until amber
-pour water on sugar, and keep stirring and heating until clumps liquefy
-whisk in cocoa
-stir in chocolate, continuing to stir until melted
-stir in milk
-keep on heat until the first bubble pops on the surface
-remove from heat and whip (with a whisk or a stick blender) until slightly frothy
notes:
-you can make it with all milk, if you want less chocolate intensity.
-you can make it without the cocoa, if you want to mellow the chocolate flavor. if so, reduce sugar to 1/4 cup.
-you can dispense with the caramelization (if you don't caramelize, it will be a bit sweeter).
