Mix together everything EXCEPT for the butter until the dough comes together - 5 minutes on KitchenAid speed 2 or spiral mixer on lowest speed.
Add softened or pounded butter. Mix until you achieve an improved mix. This varies based on your mixer. On my spiral mixer, this takes 4 minutes on speed 2 (high). On a KitchenAid, it might take longer.
Divide into 100g (3.5oz) pieces, roll into a ball and allow to rest covered for 15 minutes.
Roll out the balls into flattened discs (approximately 1/4" thick). Place into the baking tray.
Egg wash the buns and place inside a sealed bag to prevent drying. Proof for 2 hours at 80°F.
Set your oven to 350°F about an hour before baking.
Egg wash a second time. Garnish with sesame seeds (optional). Bake for 18-20 minutes (350°F, convection). Rotate in the oven once or twice during the bake for more even browning.
Allow to fully cool out of the pan before slicing.