Make the dough: In a large mixing bowl, using a stand mixer fitted with a whisk attachment, combine milk, sugar, and yeast and stir to combine. Let sit for 5-10 minutes until it starts to get foamy on the surface.
Add eggs, butter, and salt and whisk to combine.
Replace whisk attachment and attach a dough hook. Add 3 ½ cups flour and stir on medium-low speed until the dough comes together. The dough should be a bit sticky to touch but shouldn't stick to the bowl anymore. If it does stick to the sides of the bowl after a few minutes of kneading, add 1 tablespoon of flour at the time (up to 4 cups in total) and mix on low speed until you reach this point. But don't add too much flour or your Chocolate Rolls will be dry.
NOTE: How much flour you need depends on the humidity and temperature where you live, as well as the size of the cups (not every cup is equal and as accurate as a kitchen scale). Make sure that you stay at around 4 cups maximum.
Then turn on medium speed and knead for about 5 minutes. Transfer dough to a lightly greased bowl (brush a few drops of oil in a bowl or use a non-stick spray) and lightly grease the top of the dough. Cover loosely with a dry towel and let rest at room temperature for about 10 minutes.
Make the filling: In a small bowl, stir together brown sugar, cocoa, and cinnamon. Set aside.
Preheat oven to 200°F (100°C). Line a baking sheet with parchment paper. Set aside.
Roll dough into a 20x18 inch (50x45cm) rectangle. Spread the butter all over it, leaving a 1-inch (2,5cm) border at the long side where you end up rolling. Sprinkle sugar mixture and chocolate on top of the butter evenly. Roll-up long side tightly, cut into 12 equal-sized pieces and transfer to the prepared baking sheet. Don't cover rolls. Turn off preheated oven and place rolls in the oven to rise for about 30 minutes, until doubled in size. Leave the wicket ajar.
Remove rolls from the oven, store at room temperature and preheat oven to 375°F (190°C). Bake for about 20-25 minutes until lightly browned. After 10-15 minutes of baking, place parchment paper on top of the rolls to prevent them from heavy browning.
Make the frosting: In a medium mixing bowl, using a handheld or stand mixer fitted with a whisk attachment beat butter and cream cheese until creamy. Add powdered sugar and stir to combine. Stir in cocoa until well combined. Stir in 1 tablespoon milk at the time until you reach the desired consistency. I added 2 tablespoon
Remove rolls from the oven, let cool for 5-10 minutes and spoon frosting on top of the rolls when they are still warm. I recommend eating the rolls warm. They will stay fresh and soft in an airtight container in the refrigerator for up to 3 days. Reheat leftover rolls in the microwave for about 20 seconds before serving.