To Make the Sponge:

1. Warm milk to 85°F-90°F.  Add to the bowl of your stand mixer.  Add yeast and stir with a rubber spatula to combine.
2. Add all-purpose flour and stir completely with a rubber spatula to combine.
3. Cover and allow to rise for 30-60 minutes, or until the sponge is full of holes/bubbles and is one solid piece.

To Make the Dough:

1. Cut the butter into 1 tbsp cubes and set aside.  You won’t need them until the rest of the dough has come together, but you want them to be a soft room temperature before they’re added to the dough.
2. Add granulated sugar, eggs, egg yolks, and about 2 cups of the all-purpose flour to the sponge.  Stir the ingredients with the flat beater of your stand mixer until combined, and the ingredients are starting to stick together.
3. Switch to the dough hook of your stand mixer, and begin kneading with the dough hook.  Slowly add additional flour, about 1/8 of a cup at a time, until the dough starts to come away from the sides of the bowl.  You might not need all of the flour that the recipe calls for.
4. When the dough comes away from the sides of the mixing bowl, add flour, 1 tbsp at a time, still kneading for at least a minute between additions.  The goal is to have a slightly tacky dough that does come away from the sides of the bowl.
5. If you use all of the flour in the recipe, you should not need more than 3-4 more tablespoons of flour total.  At this point, the dough is “finished” when it is ever-so-slightly tacky to the touch, but not sticky.  It should also pass the windowpane test at this point, before you incorporate the butter.
6. Once the dough passes the windowpane test (the first time), begin adding the butter, one tablespoon at a time.  This is the longest part of the dough-making process, so pack your patience!  Allow the dough to fully incorporate each tablespoon of butter before adding the next one.  The bowl will likely get a buttery coating during this process.  That is normal!
7. When all of the butter is incorporated, allow the dough to knead for another 5-7 minutes on low speed.  The dough is complete when it easily passes the windowpane test (again!) and is very pliable.
8. Spray the mixing bowl with a light coating of cooking spray, and allow the dough to rise, covered with plastic wrap (with a small hole to vent gases), for 45 minutes to an hour, or until doubled in size.  You can also use the finger poke test so that you can decide whether it needs a few more minutes.
9. Gently de-gas the dough by pressing down on it in the mixing bowl.  Use your fingers to shape the dough into a rough rectangle on your work surface, with the long side of the rectangle facing you.
10. Use a rolling pin to roll the dough to about 1/2” thickness.  
11. Brush melted butter onto the dough.  Do not be shy with the butter!  But leave butter off of the top 1.5” of the rectangle.  This helps the dough stick to itself when you’re sealing it!
12. Sprinkle the brown sugar/cinnamon filling over the top of the buttered part of the dough.  Use all of it!  You want that ooey gooey goodness in your cinnamon rolls!  Press down on the cinnamon/sugar filling once it’s sprinkled over the top of the dough.
13. Starting with the long side of the rectangle that is facing you, tightly roll the cinnamon roll.  It probably won’t be even, but that’s okay!  Work slowly and make sure that the roll is as tight as you can possibly make it.
14. Trim the edges to make the roll an 18-inch log.  Cut the log into 1.5” rolls, and place them in a lightly greased 9”x13” baking pan.  
15. Cover the baking pan with plastic wrap and allow the cinnamon rolls to proof for about 45 minutes.  While the cinnamon rolls are rising, heat your oven to a true 350°F.
16. Bake the cinnamon rolls in a 350°F oven for 20-25 minutes, or until an instant-read thermometer reads 200°F in the center.
17. While the cinnamon rolls are baking, make the glaze by first adding the room-temperature cream cheese to a medium bowl and mixing with a hand mixer until the cream cheese is totally smooth.  Add the confectioner’s sugar, fine sea salt, vanilla extract, and whole milk and mix until the mixture is smooth and creamy.  Add to the cinnamon rolls immediately after taking them out of the oven.
18. Enjoy!