In a medium bowl, combine 1 cup of light brown sugar, 1/4 cup of black cocoa powder, and 2 teaspoons of ground cinnamon. Mix well with a fork until integrated and a uniform filling forms.

In a large mixing bowl, whisk together 3 1/4 cups of all-purpose flour, 1/2 cup of unsweetened cocoa powder, 2 teaspoons of instant dry yeast, 1 teaspoon of fine salt, and 1 tablespoon of granulated sugar.

Microwave 1 cup of whole milk, 1/4 cup of granulated sugar, and 1/4 cup of unsalted butter until warm, about 30-45 seconds. Stir gently to dissolve the sugar.

Pour the warm mixture into the dry ingredients and add 1 large room temperature egg. Mix with a wooden spoon until a sticky dough begins to form.

Cover the bowl with a dish towel and let the dough rest at room temperature for 15 minutes.

On a floured surface, turn out the dough and roll it into a large rectangle, about 12x18 inches.

Spread 1/4 cup of softened unsalted butter evenly over the rolled-out dough.

Sprinkle the prepared chocolate filling mixture evenly over the buttered portion of the dough.

Starting from the long side, tightly roll the dough into a log shape, pinching the sealed edge to secure it.

Cut the rolled dough into 9 equal pieces using dental floss or a sharp knife.

Place the cut rolls in a greased baking pan. Cover with plastic wrap and let rise in a turned-off oven for 30 minutes.

Preheat the oven to 350°F (175°C) after the rolls have risen.

Bake the rolls for 26-32 minutes until golden brown and slightly gooey.

While the rolls are baking, melt 1/4 cup of unsalted butter with 1/2 cup of unsweetened chocolate chips and 3 tablespoons of whole milk. Stir in 1 cup of powdered sugar and 1 teaspoon of vanilla extract until smooth.

Drizzle the chocolate glaze over the top of the rolls once cooled slightly.