Giant Cinnamon Roll Cake

A super light and fluffy cinnamon roll, made giant.

In a microwave safe measuring cup, heat the milk to 100°F / 38°C. Whisk in the yeast and the sugar. Set aside until the mixture begins to foam. (~5 minutes) In the meantime, make the tangzhong.
In a small saucepan over medium heat, continuously stir together the flour and milk until the mixture and thickens into a thick slurry. Take off the heat and set aside. Alternatively, whisk together the flour and milk in a microwave safe bowl. Microwave in 30 second intervals, stirring after each, until the mixture becomes a thick slurry.
Add the flour, salt, egg, butter, tangzhong and yeast mixture to the bowl of a stand mixer fitted with the dough hook attachment.
Knead the mixture on medium speed for ~15-20 minutes. The dough is ready when it is no longer sticking to the sides or bottom of the bowl, and passes the windowpane test.*
Once the dough is done kneading, shape the dough into a ball and place it back into the mixing bowl. Cover the mixing bowl with plastic wrap, and place it in a warm area to rise until doubled in size (~1 hr.)**

Generously butter a 8" cake pan. Crumple up some parchment paper, then un-crumple it and place it into the buttered cake pan, making sure it sticks to the bottom and sides. Set aside.
In a small bowl, mix together the brown sugar and cinnamon and set aside.
Once the dough has finished rising, lightly punch it down to remove any excess air in it. Transfer the dough to a clean and lightly floured surface, then roll it out to a 12″ x 16″ (30 x 40 cm) rectangle.
Melt the butter, then spread it over the dough. Then, sprinkle the cinnamon sugar over the butter in an even layer, rubbing the sugar into the butter.
From the longer side, cut the dough into 6 two inch strips.
Roll up one of the strips as you would with a standard cinnamon roll and place it into the center of your prepared pan.
Pick up another strip of dough and coil it around the center cinnamon roll. Repeat until you have used up all six strips of dough.
Lightly cover the pan with a towel, and let the cake rise in a warm environment until doubled in size (~30 minutes).
Preheat the oven to 350°F / 175°C.
(Optional, for browning) Make an egg wash by whisking together an egg with 1 tbsp. milk, then brush it over the cake.
Bake for 25-30 minutes, until the top of the cake is golden brown and the internal temperature of the cake has reached 180°F / 82°C.

In a small bowl, beat together the cream cheese until smooth. Then mix in the powdered sugar, followed by the milk and vanilla.
Spread the icing over the warm cinnamon roll cake, then serve and enjoy!