In a medium saucepan, add 1 cup water and 2 tablespoons of high quality cocoa powder. Set over medium high heat on your stove and use a whisk to incorporate the powder into the liquid. Bring the mixture to a boil, whisking occasionally.
Once the water is at a rolling boil, turn the heat down to medium low. Being careful not to splash yourself.
Add all the remaining ingredients. Be sure when adding the salt, to start with a dash of kosher salt.
Whisk all the ingredients well. Let the mixture come to a low and very gentle simmer over medium low heat, it should take a few minutes. If the mixture starts to boil, turn to a low heat setting.
Whisk occasionally. Once the mixture has started to low simmer, continue for 2-3 minutes.
Depending on your preferences, you might want to add more dark chocolate (this will make your hot chocolate richer and thicker). If you add more chocolate you will need to whisk more and heat it a little longer until chocolate melts and is incorporated.
Ladle the hot chocolate into 4 warmed mugs, top with whipped cream or mini marshmallows!