In a large mixing bowl (bowl of the stand mixer), combine instant yeast, warm milk and sugar. Stir to combine and let it sit for a few minutes. Bubbles should appear at the surface. (See Note 1)
In a small bowl, whisk 1 egg (save the other egg for later), and pour into large mixing bowl with yeast mixture. Then add melted butter and vanilla extract to the large mixing bowl. Stir to combine.
Attach dough hook to stand mixer and place bowl on stand mixer. Add flour, cinnamon powder, cocoa powder and salt to mixture. Knead dough. (See Note 2)
Press a finger onto the dough to make a small indention, dough should not stick to finger, but it shouldn't be dry either. If it sticks to your finger, you want to add a little bit more flour. Do not add too much flour so that your dough isn't too dry.
Transfer dough to flat floured surface. Flatten it and sprinkle chocolate chips on dough. Knead dough to fold in chocolate chips.
Form dough into a large ball and place on a greased large mixing bowl. Cover and let it rise for 1-2 hours, or until dough doubles its original size.
Punch dough to release the air. Transfer dough to floured surface and slice dough into 12 equal pieces (start by slicing it into half, and slice each halves into halves...and keep going until you get 12 pieces)
Roll each piece into a small ball, and line them up on a greased 9'x13' baking dish.
Cover and let dough balls rise for 1 hour.
Pre-heat oven to 350°F.
Crack and whisk the other egg into a small bowl, and brush the tops of the buns with egg wash.
Bake for 25 minutes.
Remove from oven and let the chocolate buns rest so that it comes to a complete cool (30 minutes to an hour).
Combine all the ingredients for the icing in a medium mixing bowl. Add additional few drops of milk at a time if needed - be careful not to add too much. If icing isn't thick, the crosses will smear.
Transfer icing into a piping tube (or a zip lock bag with one of the corners snipped), and draw crosses on top of the chocolate buns.
Serve and enjoy!