In a large mixing bowl, whisk together 2 cups of all-purpose flour, sugar, instant yeast, and salt until well combined.
In a separate bowl, beat together the warm milk, melted butter, and egg until thoroughly blended.
Gradually add the wet ingredients into the dry mixture, stirring gently until a cohesive dough begins to form.
Continue adding the remaining ½ cup of flour, little by little, until the dough becomes soft and slightly sticky. Transfer the dough to a floured surface and knead for about 5-7 minutes, or until smooth and elastic.
Place the kneaded dough into a greased bowl, cover it with a damp cloth or plastic wrap, and allow it to rise in a warm area for approximately 1 hour, or until it has doubled in size.
While the dough is rising, create the filling by combining cocoa powder, ground cinnamon, and brown sugar in a small mixing bowl. Stir until the mixture is evenly mixed.
Once the dough has risen, transfer it to a floured surface and roll it out into a large rectangle, about 16x12 inches in size.
Brush the surface of the rolled-out dough generously with melted butter, then evenly distribute the cocoa-cinnamon-sugar mixture over it, ensuring full coverage.
Sprinkle the semi-sweet chocolate chips evenly across the filling for an extra layer of decadence.
Starting from one of the long edges, carefully roll the dough tightly into a log shape. Once rolled, cut the log into 12 equal portions using a sharp knife or a bench scraper.
Arrange the slices in a greased baking pan, spacing them slightly apart. Cover the pan and let the rolls rise for an additional 30 minutes.
Preheat your oven to 350°F (175°C) while the rolls are rising. Bake the rolls for 20-25 minutes, or until they are golden brown and puffed.
For the icing, whisk together the powdered sugar and 2 tablespoons of milk in a small bowl until smooth and creamy. Adjust the thickness if necessary.
Once the rolls are baked to perfection, remove them from the oven and generously drizzle the icing over the warm rolls offering a luscious finish.
Allow the rolls to cool slightly in the pan before serving.