To make the dough: Weigh your flour; or measure it by gently spooning it into a cup, then sweeping off any excess. Combine the flour, dry milk, potato flour, sugar, salt, and yeast in a large mixing bowl. Add the butter and lesser amount of water then mix and knead everything together—by hand, mixer or bread machine set on the dough cycle—to form a smooth, elastic dough, adding more water if necessary. If you're kneading in a stand mixer, it should take 7 to 10 minutes at second speed, and the dough should barely clean the sides of the bowl, perhaps sticking a bit at the bottom. In a bread machine (or by hand), it should form a smooth ball.