Heat milk and water until warm (100º to 110ºF).  Add yeast and allow to rest for 5 minutes.

Combine 2 cups flour, cocoa, sugar and salt in a large mixer bowl.  Add yeast mixture, butter, eggs and vanilla.  Beat for 2 minutes on medium speed.  Add enough remaining flour to form a soft dough.   

Knead on a lightly floured surface for 6 to 8 minutes, until dough is smooth and elastic.  Shape dough into a ball and place in a greased bowl, turning once to coat.  Cover bowl with plastic wrap that has been sprayed with nonstick spray. Refridgerate for at least 4 hours or over night. 

Punch dough down.  Roll dough into a 16 x 12-inch rectangle.  Spread butter evenly over dough.  Whisk together sugar, brown sugar and cinnamon.  Sprinkle mixture evenly over butter followed by chocolate chips. 

Roll dough up tightly, starting with the short end.  Pinch seam to seal.  Cut dough into 18 equal sized rolls.  Place rolls in one greased 13 X 9-inch and one greased 8 x 8-inch baking pan.  Cover and let rise until doubled, about 1 hour.  

Bake 20 to 25 minutes in a preheated 375ºF oven.  Cool pans on wire rack. 

Mix powdered sugar, butter, milk and vanilla in a medium bowl until smooth.  Spread over warm rolls.

Recipe Note: Dough will be rather soft and sticky, and will take a little extra time for rolling and cutting rolls.