To make the dough: In the bowl of a stand mixer fitted with the dough hook, add the yeast, ½ teaspoon cane sugar, and warm water. Stir to combine and let sit for 3 to 5 minutes or until bubbly.
In a medium pot over medium heat, add the butter and milk. Stir until completely melted, remove from heat.
Add the flour, hot chocolate mix, and salt to the mixing bowl in that order. Add the egg and milk mixture and knead on speed 2 to 4 for 5 minutes, until it's smooth.
Place the dough in a greased bowl, add cover the bowl with plastic wrap and let rise for 1 to 3 hours or until doubled in size.
Preheat the oven to 350°F.
To make the filling: In a bowl, add the butter, cane sugar, and hot chocolate mix and stir to combine completely.
Generously flour your work surface, roll out the dough to a rectangle that is about 12 x 16-inches. Using a spatula spread the butter and cocoa mixture all over the rolled out dough.
Starting at the larger side, fold the dough over and start to roll the dough until it is completely rolled into a log. Trim off each of the ends, then cut the dough log into 8 cinnamon rolls. Place in a greased baking dish.
Bake for 35 minutes or until golden brown. Allow the rolls to cool for about 10 minutes.
Spread the marshmallow creme on top of the rolls.
Using a chocolate shaver, shave the dark chocolate bar on top of the rolls.
Store in the fridge for up to 3 days.