Put all the ingredients except the butter into the bowl of stand mixer with the dough hook attachment. Mix on low speed until dough becomes strong and gluten has developed, 40 to 45 minutes. [Dough should pass the windowpane test; see Notes.]
Add the butter and continue kneading until well combined.
Let it rise until doubled in size.
Remove the dough and gently press the top with your hand to release the gas. Divide into 2 equal portions (about 218 grams each), and shape each into a ball. Cover with a cloth and let rest at room temperature for 15 minutes.
Roll out each dough ball with a rolling pin into a rectangle, about 23x13cm (9x5 inches).
For each dough ball, fold in both sides (about one-fourth of the width) toward the center, then roll it up from one end [see photos below].
Place the two rolled doughs into the loaf pan, positioning them along the edges if desired. Cover with plastic wrap and proof at 35°C (95°F) for 45 to 60 minutes or until the dough rises to about 1.5cm (1/2 inch) below the top of the pan.
Bake in a preheated oven at 200°C (390°F) for 30 minutes or until golden brown. After baking, take the pan out of the oven and firmly tap it on the table while still in the pan. This helps release the steam trapped inside the bread, preventing it from shrinking when you remove it from the pan.