Tangzhong: 

1. Whisk together the flour, milk and 2 tablespoons (27g) of water in a medium saucepan over medium heat. Continue to cook, whisking constantly for about 1-3 minutes or until a very thick paste forms. 
2. Remove to a bowl and cool to room temperature. 

Bread Dough:

1. Stir together the warmed milk and yeast and let sit for 10 minutes or until the yeast starts to foam.

1. Fit a stand mixer with the dough hook. Add all the dry ingredients to the bowl and mix for a few seconds to combine. 
2. Turn the machine off and add the cooled tangzhong, yeast mixture and 1 egg. Mix on low speed, scraping the sides as needed, until a dough forms. Increase the speed to medium-low and add in the butter, 1 tablespoon at a time, making sure the butter is fully incorporated before adding more. Scrape down the sides of the bowl as needed while mixing in the butter. Once the butter is incorporated, continue to knead the dough at medium-low speed for 5-7 minutes until smooth.
3. Remove the dough from the stand mixer and form it into a ball. The dough may be a little sticky, this is fine. If you are having a really hard time working with the dough you can coat your hands in a little flour. Place the dough on a clean work surface and roll the ball in a circular motion between your palms, keeping constant contact with the work surface, until the dough becomes a taut ball.  
4. Lightly grease a medium bowl with cooking spray. Add the dough and cover with a damp towel. Let the dough rise at room temperature until doubled in size, about 1-2 hours. 
5. Punch the dough down and then add it to a lightly floured work surface. Divide the dough into 9 equal pieces that are about 75 grams each.
6. Lightly grease a 9x9” (22x22cm) baking dish with cooking spray. Using the same method as earlier, roll each piece of dough into a taut ball; this time covering the dough with the palm of your hand and moving it in a circular motion around the dough, keeping constant contact with the work surface. Place the dough into the prepared baking dish. Repeat with the remaining dough until you fill the pan with 3 rows of 3 dough balls. Cover with a damp towel and let proof until puffed and nearly doubled in size, another 1-2 hours.
7. Preheat your oven to 350℉ (175℃). 
8. Whisk together the remaining egg and a splash, about 2 tablespoons, of whole milk. Brush the egg wash over the top of the rolls. 
9. Bake the rolls in the preheated oven for 28-30 minutes or until they are a rich golden brown, puffed and cooked through. 
10. Remove from the oven. Immediately brush with melted butter and top each roll with a sprinkling of flaky salt.