In the bowl of your stand mixer, add in your flour, sugar and salt for the cinnamon roll. Whisk to combine then add in your 6 tablespoons of butter. Using your impeccably clean hands, mix together the butter with your flour mixture. You should end up with small lumps in your batter.
Crack your two whole eggs and extra egg yolk into a small bowl and set aside.
In a microwaveable bowl or cup, add your milk and heat in the microwave for about 40 seconds until it's slightly warmer than lukewarm (If you have an instant read thermometer, you should see about 100 degrees Fahrenheit.) Add in your instant yeast and whisk for about 30 seconds. Let the milk/yeast sit for a few minutes, then whisk for another 30 seconds. You want the majority of the yeast to dissolve.
With a dough hook attachment on your stand mixer, mix your flour on medium low speed and add in your yeasted-milk and your eggs. Continue on medium low speed for a few minutes or until your dough comes together.
Remove your dough from the bowl and knead into a ball on a lightly floured surface for about 30 seconds. Your dough will still be tacky or sticky, but you should be able to touch it without it sticking to your hands. Place the dough into a lightly buttered dish or bowl (I just used the glass pan I cook the rolls in), cover, and let rise for an hour and a half at room temperature.
Prepare your filling by adding 1 cup of light brown sugar, 1/2 cup of granulated sugar, and three tablespoons of cinnamon to a small bowl and whisk to combine. Set Aside.
Once your dough has risen for an hour and a half, prepare a large surface with flour and roll out your dough into a long thin rectangle, measuring about a 1/4 inch thick. If you prefer more bread-to-filling ratio, keep your thickness to about 1/2 inch.
Using your impeccably clean hands, spread enough butter to cover the entire rectangle generously, and then top with your filling mixture, making sure every inch (including the edges) is covered.
Starting on one of the long sides of the rectangle, tightly roll your dough into a long log (pictured above), and then slice into 1 1/2 inch pieces using a scalloped (NOT serrated) knife.
Lay your pieces (not touching) in a buttered baking dish, cover, and let sit for another 30-45 minutes at room temperature.
Preheat your oven to 375 degrees Fahrenheit.
Prepare your icing by combining 1 1/4 cups sifted powdered sugar and a 1/4 cup heavy whipping cream together either by hand or with a hand-mixer. Add in the light corn syrup, vanilla, and one tablespoon of butter (softened) and mix until combined.
After your Cinnamon rolls have rested again, bake them at 375 degrees Fahrenheit for 15-20 minutes. 15 if you like ooey-gooey centers, 20 if you like them done.
Let rolls cool for 10-15 minutes, top with icing, serve and enjoy!