01 - Combine flour, cocoa powder, yeast, sugar, and salt in a large mixing bowl.
02 - Pour in warm milk, melted butter, and egg. Stir until a sticky, uniform dough forms.
03 - Knead by hand on a floured surface or with a stand mixer for 8-10 minutes until smooth and elastic.
04 - Transfer dough to a greased bowl, cover with plastic wrap or a towel, and let rise in a warm, draft-free area until doubled in volume, approximately 1 hour.
05 - Punch down risen dough and roll out on a lightly floured surface into a 16x12-inch rectangle.
06 - Spread softened butter evenly over the entire surface of the rolled dough.
07 - Mix brown sugar, cocoa powder, and cinnamon in a small bowl until well combined.
08 - Sprinkle the sugar-cocoa mixture evenly over the buttered dough, then distribute chocolate chips on top.
09 - Starting from one long edge, roll the dough tightly into a log. Cut into 12 equal pieces using a sharp knife or unflavored dental floss.
10 - Arrange rolls in a greased 9x13-inch baking dish. Cover and let rise until puffy and visibly increased in size, about 30-45 minutes.
11 - Heat oven to 350°F during the final minutes of the second rise.
12 - Bake rolls for 22-25 minutes until set and lightly browned on top. Avoid overbaking to prevent dryness.
13 - While rolls cool slightly, whisk powdered sugar, cocoa powder, 2 tablespoons milk, and vanilla extract until smooth. Add additional milk as needed for desired consistency.
14 - Drizzle chocolate glaze generously over warm rolls. Serve immediately while still warm for best texture and flavor.