Activate the yeast: Warm the milk to about 110°F. In a small bowl, combine the warm milk with the instant yeast and granulated sugar. Let sit for about 5 minutes until frothy.

Make the dough: In a mixing bowl, whisk together flour, sugar, salt, cocoa powder, and food coloring. Add activated yeast mixture, butter, egg, and buttermilk. Mix until a soft dough forms.

Knead the dough: Transfer dough to a floured surface. Knead for 7-8 minutes until smooth and elastic. Place in a greased bowl, cover with a towel, and let rise in a warm area for 1 hour.

Prepare the filling: Mix brown sugar, granulated sugar, cocoa powder, and cinnamon in a medium bowl.

Roll out the dough: Punch down the risen dough and roll into a 12x16 inch rectangle. Spread softened butter and sprinkle filling evenly.

Cut the rolls: Roll the dough into a log and slice into 12 equal pieces. Place in a greased baking dish.

Second rise: Cover rolls with a towel and let rise for 30-40 minutes until puffy.

Bake: Preheat oven to 350°F. Bake rolls for 20-25 minutes until golden brown.

Make the glaze: Whisk together powdered sugar, milk, and vanilla until smooth.

Glaze and serve: Let rolls cool for 5 minutes, then drizzle glaze over them and serve.