Grease a 9×13-inch baking pan really well. Whisk flour, sugar, instant yeast, and salt in a bowl and set aside.
6 ⅓ cups all purpose flour, 4.5 teaspoons instant yeast, 5 tablespoons granulated sugar, 1.5 tablespoons kosher salt
In the bowl of a stand mixer or a separate large bowl, whisk together the two eggs and an egg yolk.
2 large eggs, 1 large egg yolk
Gently heat milk and butter to between 115-120°F. Whisk to combine. Combine the eggs, milk, and butter, whisking until smooth.
1 ¼ cup + 3 tablespoons whole milk, 8 tablespoons unsalted butter
Add about ⅓ of the dry ingredients to the wet, and whisk until smooth. This just helps the mixer out a little bit and gets the process going. Add the remaining dry ingredients to the stand mixer. Knead the dough for 7-10 minutes, it's until it's soft, pliable, and no longer clings to the sides of the bowl. The dough should pass the windowpane test, and that's how you know it's ready. Roll the dough into a smooth ball shape, then place it seam side down into a clean bowl with oil. Rub the top with a bit of oil, then cover with a towel or plastic wrap and place the bowl in a warm place to rise for 60-90 minutes. Meanwhile, prepare the filling.
The dough is ready to roll and shape once it has doubled in size, and leaves an indent where pressed.