03By Hand: Take the flour in a big bowl . Make a well in the middle add the cooled tangzhong ,yeast, sugar and the beaten egg . Stir with a wooden spoon until all the flour is moistened .Cover with a plastic wrap or a wet towel and let the dough rest for 20 minutes .
04Uncover , transfer to a lightly floured surface . Sprinkle the salt on top and knead gently for 5 minutes . Add a couple of tablespoons more of the flour if the dough is too sticky. Add the softened butter 1 tablespoons at a time and knead gently to incorporate well. As you need the dough becomes very soft and pliable . Transfer the dough to a buttered bowl. cover and let it rise for an hour or so till doubled in volume .
05In the mixer: Take most of the flour in the stand mixer's bowl. Add the egg , activated yeast, and tangzhong to it. Fit the paddle attachment and set the machine to the lowest (stir) and mix for about 1 minute until all the flour is moistened.
06Change to the dough hook and knead for 1 minutes. If the dough is too sticky add the remaining flour slowly while kneading. Once the dough begins to pull away from the sides of the bowl (1 to 2 minutes) add the softened butter and sugar and salt. Keep kneading for 3 to 4 more minutes until the dough looks glossy. It should feel slightly warm and supple when touched. Transfer the dough to a buttered bowl. cover and let it rise for an hour or so till doubled in volume .
07Shape: Generously butter the bread pan or line it with parchment paper.Punch down the dough and divide into 4 equal size portions . Form each portion into a ball.
08Working with one ball at a time . Roll it out into rectangle . Fold the opposite sides quarter way in to meet at the middle . Roll this from one end to form a log . Pinch to close . Transfer the log into the buttered bread pan seam side down . Repeat with the other balls and arrange logs neatly in the pan .Cover and let rise for 30 to 45 minutes in a warm place , until it has more than doubled and peeking out over the top of the pan .
09Preheat the oven to 350ºF(175ºC) . Make the egg wash by mixing the egg and milk and beating well .Brush the top of the bread with egg wash and transfer to the preheated oven .Bake for 30 to 40 minutes . Check and adjust temperature at 25 minutes to prevent over browning .
10Cool in the pan for 10 minutes. Transfer to a cooling rack and let cool for at least 1 hr before slicing .