If you're using instant yeast, add it right to the flour mixture. If using active dry yeast, dissolve it with the lukewarm milk for 5 minutes until bubbling, the bloomed yeast will go in with the wet ingredients.
Measure the bread flour by spooning it into a measuring cup and leveling off any excess. Add the flour to the bowl of a stand mixer with the instant milk powder, sugar, salt, and instant yeast.
Using the dough hook, mix together the dry ingredients at low speed.
Pour in the milk, beaten egg.
Melt 6 tablespoons of butter and add it to the mixing bowl with the other ingredients.
Mix on medium speed and knead everything together until the dough is barely pulling away from the sides of the bowl, but still sticking to the bottom, this takes 7-8 minutes. Do not be tempted to add more flour!
After mixing, sprinkle the work surface lightly with flour. Scoop the dough out onto the work surface and knead it into a smooth ball. The dough should be very soft, but not sticky.
Place the dough in a lightly greased bowl and cover the dough with plastic wrap. Allow the dough to rise, at room temperature, for 1 to 1 1/2 hours, or until it's nearly doubled in size. Note: Rising may take longer if the house is super cold.
Once doubled, gently deflate the dough, and divide into 16 pieces, get that as equal as you can. Pinch the corners of the dough together to make a rough ball, and then roll each piece on the work surface into a smooth ball.
Next, Flatten each ball of dough to 1/4” thick circle about 3 1/2 “ wide. Use your finger or a wooden spoon handle to make a crease across the middle of the dough. This will keep the rolls from being too thick when folded in half.
Melt the remaining 3 tablespoons of butter and brush the dough with melted butter. Save any leftover melted butter for the top.
Fold the dough in half on the crease you made and gently press to adhere the two halves together. Tip: if the dough is giving you a hard time, let it rest for 10-15 minutes to keep it from stretching back on you.
Line up your rolls in a 13x9" pan. Arrange 3-4 rows of 4 in the pan, with the long side of the rolls lined up with the long side of the pan. If the rolls don’t all fit that way, fit them in where you can.
Brush the tops of each roll with the remaining butter. Cover the pan with lightly greased plastic wrap. Let the dough rise until very puffy, and the dough does not spring back when poked--about 45-60 minutes.
While the dough is rising, preheat the oven to 350°F and mix together 1 egg with 2 teaspoons of milk to make the egg wash.
Brush the rolls with the egg wash and sprinkle on 1 teaspoon of flaky salt. Bake the rolls for 20-25 minutes until the crust is golden brown, and the interior temperature measures 190°F on a digital thermometer. Serve warm and enjoy!