In a large bowl, whisk together warm milk, melted butter, and granulated sugar. The mixture should be just warm, registering between 100-110˚F (40˚C). If hotter, allow to cool slightly.
Sprinkle the yeast evenly over the warm mixture and let sit for 1 minute.
Add 4 cups of all-purpose flour to the milk mixture and mix with a wooden spoon until just combined.
Cover the bowl with a towel or plastic wrap and set in a warm place to rise for 1 hour.
Preheat oven to 325˚F (160˚C).
After 1 hour, the dough should have nearly doubled in size. Remove the towel and add an additional ¾ cup of flour, the baking powder, and salt. Stir well, then turn out onto a well-floured surface.
Knead the dough lightly, adding additional flour as necessary (about ½ cup), until the dough just loses its stickiness and does not stick to the surface.
Roll the dough out into a large rectangle, about ½-inch thick. Fix corners to make sure they are sharp and even.
In a small bowl combine the filling ingredients and stir to combine.
Spread the filling mixture evenly over the rolled out dough, spreading right to the edges.
-Using a pizza cutter, make 3 horizontal cuts to divide the dough into four long, evenly sized strips.
Starting from the bottom, roll the first strip up right to left. Take the first roll and place it back on top of the next strip, starting again on the right side and rolling up right to left, building on the first. Continue with the remaining two strips until you have a giant cinnamon roll.
Place the giant cinnamon roll in the prepared cast iron or cake pan and cover with plastic wrap. Place in a warm spot and leave to rise for 30 minutes. The cinnamon roll should expand to the edges of the pan during this time.
Bake for 45 minutes. Cover the cinnamon roll with foil to prevent the outside from burning, and bake for an additional 35 minutes.
While the cinnamon roll is baking, prepare the frosting. In a medium-size mixing bowl, whisk together cream cheese, butter, vanilla, whole milk, and powdered sugar, until smooth.
Remove the cinnamon roll from the oven and let cool in the pan for at least 20 minutes. Once cool, remove from pan and drizzle frosting over the roll before serving.
