01 - Combine flour, cocoa powder, instant yeast, granulated sugar, and salt in a large mixing bowl.
02 - Pour warm milk, melted butter, and egg into the dry ingredients. Stir until a sticky, shaggy 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 towel, and let rise in a warm place until doubled, about 1 hour.
05 - Punch down risen dough and roll into a 16x12-inch rectangle on a lightly floured surface.
06 - Spread softened butter evenly over the surface of the rolled dough.
07 - Stir together brown sugar, cocoa powder, and cinnamon in a small bowl until well combined.
08 - Sprinkle the sugar-cocoa mixture over the buttered dough, then scatter chocolate chips on top.
09 - Starting from one long edge, roll the dough tightly into a log. Slice into 12 equal pieces.
10 - Place rolls in a greased 9x13-inch baking dish. Cover and let rise until puffy, 30-45 minutes.
11 - Heat oven to 350°F.
12 - Bake for 22-25 minutes until rolls are set and lightly golden on top.
13 - While rolls cool slightly, whisk powdered sugar, cocoa powder, milk, and vanilla until smooth.
14 - Drizzle chocolate glaze generously over warm rolls before serving.