In the bowl of a stand mixer fitted with a dough hook, combine the flour, cocoa powder, sugar, yeast and salt.

Mix in the butter until the mixture is crumbly, then stir in the egg and water and knead on medium speed for about 8 minutes, until the dough clears the sides of the bowl. It is a soft dough.

Transfer the dough to a large, oiled bowl. Cover with plastic wrap and let rise until doubled, about 90 minutes.

In a medium microwave safe bowl, combine the butter and chocolate and microwave for 60-90 seconds on high until melted.

Whisk in the powdered sugar, cocoa powder, cinnamon, vanilla extract and salt. Set aside.

Butter a 9x13 inch baking dish.

On a floured surface, roll the dough into a 10x15 inch rectangle.

Starting at a 15-inch edge, spread the filling onto the dough all the way to the 10-inch edges, leaving a 1-inch border unfilled at the opposite 15-inch edge.

Roll the dough from the filled 15-inch edge all the way to the unfilled edge.

Cut the log into 12 equally-sized pieces (about 1 ¼ inch thick) and arrange in the prepared pan.

Cover with plastic wrap and let rise until doubled, about 60 minutes.

Towards the end of the rising time, preheat the oven to 350°F.

Egg wash the rolls carefully and bake for 25-35 minutes, until firm and lightly brown. Set aside while you make the glaze.

In a medium bowl, whisk together the powdered sugar, cocoa powder, cream cheese and vanilla extract.

Whisk in 2 tablespoons of milk until smooth and spreadable. If it is too thick, add more milk, 1 teaspoon at a time, until you reach the correct consistency.

Spread the glaze over the warm rolls and serve.

Store leftovers in an airtight container in the refrigerator for up to 3 days. Rewarm in the microwave for 30 seconds before eating.