Place the flour (420g), dry milk powder (30g), sugar (38g), yeast (2 1/4 teaspoons), salt (3/4 teaspoon), 1 egg, 2 egg yolks, and milk (240ml) in a stand mixer bowl.
Mix on low using the paddle attachment until you have a shaggy mass and all of the flour has been hydrated.
Replace the paddle attachment with the dough hook and mix for about 2 minutes. You should have a sticky, rough dough.
With the mixer on medium speed, add the butter (113g) one piece at a time, waiting for each piece to be incorporated.
Increase the speed to medium-high and mix until the sides and bottom of the bowl are clean and you have a smooth, elastic dough that is slightly sticky.
Cover the bowl with plastic wrap and place the bowl in a warm spot to rest for about one and a half to two hours or until double in size.
Punch the dough to deflate the air, then divide it into twelve equal portions. Each approx. 70g.
Roll each piece into a dough ball and place it on a baking sheet lined with parchment paper. I used a 9x16-inch cookie sheet, but you can use a larger pan if you don't wish the buns to stick to each other.
Brush the buns with the egg wash and set a side to rest again for about 90 minutes, or until double in size.
Bake at 350F over the middle oven rack for 22-25 minutes. Until the tops are golden brown and the internal temperature is 180-200F.
Remove from the oven and allow the rolls to cool slightly before serving.