For the tangzhong, in a sauce pan, combine the Bread Flour (35 gram) and Water (168 gram). Mix with whisk or spatula until no lumps. Cook over medium-low heat, stirring consistently until the mixture becomes thicker. Once you see some lines appear, it is ready.
Remove from heat and transfer to a clean bowl to let it cool. Cool down to room temperature and use straight away or fridge for a few days. Return to room temperature before using.
Line the baking pans with parchment paper.
Whisk the Large Egg (1) and separate around 45 grams for the dough and 10 grams for the topping. Add 1 teaspoon of water to the topping whisked egg.
Add the Salt (3/4 teaspoon), Bread Flour (320 gram), Instant Dry Yeast (1 1/8 teaspoon), Brown Sugar (2 1/2 tablespoon), Milk Powder (2 tablespoon), Butter (33 gram), Milk (65 gram), whisked egg, and the tangzhong into the bowl of stand mixer.
Using the dough hook, knead until the dough comes together and is beginning to become elastic and tacky but not sticky. Tacky dough behaves sort of like a Post-it note, sticking to a surface but peeling off easily. It takes around 10 to 15 minutes. If the dough is too dry, add 1 tablespoon of milk at a time.
Let the dough rise in a warm place for 1 hour or until double in size in a large greased bowl, covered with cling film or kitchen towel. I normally leave the dough in the stand mixer’s bowl and cover with kitchen towel.
Punch down the dough to release the air. Transfer the dough to a clean floured surface then divide into 12 equal portions. Shape each dough into a ball. Flatten the dough and shape it into an oval shape. Place the buns in the prepared baking pan. Let it rise for another 50 minutes or until double in size.
Preheat the oven to 180 degrees C (350 degrees F).
Slit center of the bun with scissor. Brush with egg wash. Place the Salted Butter (30 gram) onto the slit and top with Sea Salt (to taste) and Brown Sugar (30 gram).
Bake in a preheated oven for 15-20 minutes, or until golden brown.
Remove from the oven and transfer onto a wire rack to cool. Serve and enjoy!