Add milk of choice, cocoa powder, sweetener and salt to a small saucepan over medium heat until it just begins to simmer. Taste for sweetness and adjust to taste. Make a slurry with a little konjac root powder (it's powerful stuff guys!) and a tablespoon or two of water; make sure it's completely dissolved to avoid lumps. Whisk it into the hot chocolate and cook until thickened. Feel free to adjust the quantity to yield your preferred thickness.
Serve with (plenty!) of marshmallows.
NOTE: if using arrowroot you also need to make a slurry, but xanthan gum can be added directly (works best with an immersion blender though). And chia seeds need to be blended fully to avoid any lumps.
Please note that cacao and cocoa nutrition values do vary, so check your nutrition labels (I used Valrhona!)!