Begin by sprinkling the yeast and 1 teaspoon of the sugar into the warmed milk. Give this a stir and set aside for 10 minutes until the mixture develops a foam on top.
¼ cup full fat milk, 2¼ teaspoon dry active yeast
Meanwhile in the bowl of a stand mixer fitted with a dough hook, stir together the flour, bread flour, remaining sugar and salt.
1 tablespoon superfine granulated sugar, 1 cup all purpose flour, ¾ cup bread flour, 1 teaspoon salt
Add the yeast and milk mixture to the flour mixture immediately followed by 2 eggs and one egg white (the remaining egg yolk can be reserved for a quick egg wash before baking the rolls).
3 large eggs
Knead on a low setting for 15 minutes, scraping the sides of the bowl down occasionally, until your dough has come together and is starting to pull itself from the sides of the bowl. (see note)
Add the butter a couple pieces at a time while continuing to knead. Once the butter is incorporated into the dough, continue kneading at a low setting for 15 minutes until the dough is again beginning to pull itself from the sides of the bowl.
½ cup unsalted butter
Scrape the dough into a greased bowl, cover with plastic wrap and place in the refrigerator for a slow overnight proof (about 8 hours).