1. Place warm milk in mixing bowl and sprinkle yeast over top. Allow yeast to bloom for 5-10 minutes.
2. Add brown sugar, egg plus egg yolk, and vanilla to yeast mixture. Stir to combine.
3. Add flour, instant coffee, salt, butter, and sift in cocoa powder to avoid bitter lumps.
4. Mix with dough hook on speed 2 for 6-7 minutes, scraping down sides as needed, until a soft dough forms. This is a sticky dough but if you feel it is very wet and soupy, add a bit more flour.
5. Scrape down sides, cover, and let dough rise for 60-90 minutes until doubled.
6. Turn out onto cocoa dusted surface and roll to a large rectangle.
7. Combine filling ingredients in a bowl and mix well. Spread filling over entire surface of dough. Roll dough tightly into a log and slice into 12 even pieces.
8. Arrange slices in a 9x13 baking dish and allow to rise for 60-90 minutes until puffy. Give one a poke on the side with your finger - if the dough springs back quickly they need more rising time. If it leaves an indentation, they are done rising.
9. Bake in preheated 350 degree oven for 30-35 minutes.
10. Glaze while still slightly warm.

To prepare glaze simply mix ingredients in a bowl until you reach a smooth, frosting consistency. I like to use a large whisk for this to avoid lumps. Add more milk if you like it thinner and more powdered sugar if you like it thicker.