In the bowl of a stand mixer fitted with the paddle attachment, combine the warm milk, granulated sugar, and yeast. Cover the bowl with a clean kitchen towel and let stand for 5 minutes to bloom.
2 cups milk, ⅓ cup granulated sugar, 3½ teaspoons instant dry yeast
Once the yeast is frothy, add the eggs, sugars, vanilla, and salt. Mix until fully incorporated, about 30 seconds.
3 large eggs, 2 large egg yolks, 3 tablespoons brown sugar, ½ teaspoon pure vanilla extract, 2 teaspoons kosher salt, ⅓ cup granulated sugar
Add 4 cups of flour. Mix well. Scrape down the sides of the bowl as needed.
8 cups all-purpose flour
Remove the paddle attachment and switch to the dough hook. Add the butter and mix until fully incorporated, about 2 minutes.
18 tablespoons unsalted butter
Add the remaining 4 cups of flour and knead on medium speed for 10 minutes.
Remove the dough from the bowl and shape it into a rough ball. Spray the inside of the bowl with nonstick spray. Place the dough ball back into the greased bowl, rolling it around to coat all sides. Cover the dough with a damp kitchen towel and set in a warm place to rise until doubled in size, about 1 hour.
While the dough rises, make the filling. In a small bowl, mix the sugars and cinnamon together. Set aside.
⅔ cup brown sugar, ½ cup granulated sugar, 3 tablespoons ground cinnamon
Once doubled in size, preheat oven to 350°F. Line 2 jumbo cupcake tins with jumbo cupcake liners or generously grease with nonstick spray. Set aside.