In a medium mixing bowl, combine 1/2 cup of light brown sugar, 1/3 cup black cocoa powder, and 1 tablespoon of ground cinnamon. Whisk together until fully mixed and set aside.

In a large mixing bowl, stir together 4 cups of all-purpose flour, 1/3 cup unsweetened cocoa powder, 2 teaspoons instant dry yeast, and 1 teaspoon fine salt. In a separate bowl, combine 1 cup of warm milk, 1/3 cup granulated sugar, and 1/4 cup softened unsalted butter. Pour the wet ingredients into the dry, mixing until a sticky dough forms.

Transfer the dough onto a floured surface and knead for about 5–7 minutes, until the dough is elastic and smooth. Cover with a towel and let it rest for 15 minutes.

After resting, roll the dough out into a rectangular shape, approximately 12x18 inches. Spread 1/4 cup of softened butter and evenly sprinkle the chocolate cinnamon filling over it.

Starting from one edge, tightly roll the dough into a log shape. Slice the rolled dough into 9 even pieces. Place each roll in a greased pan, cut side up.

Cover the pan with foil and place it in a turned-off oven for 30 minutes to rise.

Preheat your oven to 350°F (175°C) and bake the rolls for 26-32 minutes, until golden brown.

While the rolls are baking, melt 1/2 cup of chocolate chips, 2 tablespoons of unsalted butter, and 3 tablespoons of milk in a saucepan over low heat. Stir until smooth, then whisk in 1 cup of powdered sugar and 1 teaspoon of vanilla extract.

Once the rolls are baked, allow them to cool for about 10 minutes. Drizzle the glaze over the warm rolls.