01 - In a large bowl, combine flour, cocoa powder, instant yeast, granulated sugar, and salt. Whisk thoroughly to ensure even distribution of yeast and cocoa throughout the flour mixture.
02 - Pour warm milk (105-110°F) into the dry mixture along with melted butter and room temperature egg. Mix with a wooden spoon or stand mixer fitted with dough hook until a sticky, shaggy dough comes together.
03 - Knead the dough on a lightly floured surface for 8-10 minutes by hand, or 5-6 minutes with a stand mixer on medium-low speed. The dough should become smooth, elastic, and spring back when pressed with a finger.
04 - Transfer the dough to a lightly greased bowl, turning once to coat all surfaces. Cover with plastic wrap or a damp towel and place in a warm, draft-free area. Let rise until doubled in volume, approximately 1 hour.
05 - Punch down the risen dough to release air bubbles. Turn onto a lightly floured surface and roll into a 16x12-inch rectangle, ensuring even thickness throughout.
06 - Spread softened butter evenly over the entire surface of the dough using a spatula or pastry brush, leaving a 1/2-inch border around the edges.
07 - In a small bowl, combine brown sugar, cocoa powder, and ground cinnamon. Mix until uniformly blended and no lumps remain.
08 - Sprinkle the brown sugar-cocoa mixture evenly over the buttered dough. Scatter chocolate chips across the surface, pressing gently to adhere.
09 - Starting from one long edge, roll the dough tightly into a log. Using unflavored dental floss or a sharp knife, slice the log into 12 equal rolls, approximately 1 1/2 inches thick.
10 - Place rolls cut-side up in a greased 9x13-inch baking dish, leaving space between each roll. Cover and let rise in a warm place until puffy and noticeably expanded, 30-45 minutes.
11 - Preheat oven to 350°F with rack positioned in the center.
12 - Bake rolls for 22-25 minutes until set, puffy, and lightly golden brown on top. The centers should feel springy when gently pressed—avoid overbaking as the chocolate can become bitter.
13 - While rolls cool slightly in the pan, whisk together powdered sugar, cocoa powder, 2 tablespoons milk, and vanilla extract in a medium bowl. Add additional milk 1 teaspoon at a time until desired pourable consistency is reached.
14 - Drizzle warm chocolate glaze generously over the slightly cooled rolls. Serve warm for best texture and flavor.