Mix together the sugar, salt, and cocoa powder in a small bowl. Then, in a medium saucepan on medium heat, add your boiling water and squares of dark chocolate. Gently whisk chocolate squares around until they melt. Add in your dry ingredients: the sea salt, brown sugar, and cocoa powder and whisk them with the hot water and melted chocolate.
Whisk in your cream and cannamilk. Raise the heat and whisk vigorously until the mixture is steaming but not boiling.
Remove the mixture from the heat, stir in your vanilla extract, pour your hot cocoa into a mug and enjoy.