American Cinnamon Rolls with frosting

I am travelling in the USA for a family reunion in Utah. Before and after, I am visiting all my bros and sisters at their houses, and learning lots of new things that they are doing. My sister-in-law made these amazing cinnamon rolls. I thought she had bought them from a bakery - they are so yummy! Also, her sister had worked at a famous cinnamon roll bakery called "Cinnabon" here, and the frosting is her own version of their frosting.

Here is the recipe, makes 24 rolls:

Dough
1 .5 cups milk
3/4 cups plus 1 tablespoon sugar
1 egg
1 tablespoon salt
2 tablespoons yeast
2 cups of warm water
1/2 cup butter
9-10 cups flour

Filling
1 cup butter
2 cups sugar
3 tablespoons cinnamon

Frosting
1 1/4 cups powdered sugar
8 oz (226 g) cream cheese, softened
5 tablespoons butter, softened
1 tablespoon sour cream or buttermilk
1/2 tablespoon vanilla

Instructions:

- Scald 1.5 cups milk, 3/4 cups sugar, 1/2 cup butter for 2 minutes in the microwave
- Cool by adding 1 cup of flour, then 1 egg and 1 tablespoon of salt. Let cool.
- Dissolve 2 tablespoons yeast in 2 cups warm water and 1 tablespoon sugar, let sit 2 minutes.
- Combine yeast and sour cream (or buttermilk) mixture.
- Gradually stir in 8-9 cups flour, let double (1 to 1.5 hours)
- Divide into 2 parts, roll out 2 long rectangles (about 9 cm wide)
- Slice each rectangle into 12 rolls. Spread on filling. Let rise 1 to 1.5 hours.
- Bake at 350 degrees F (260 Celsius) for 25-30 minutes in two 9x13 inch pans.

You spread on the frosting after they have been baked in the oven.