Prepare the tangzhong. Mix together, 15g flour, and 80g of milk in a small saucepan. Put the saucepan over medium-low heat and whisk constantly. When the whisk starts to leave trails where you can see the bottom of the pan, it is done. Transfer to a small bowl and allow to cool.
In the bowl of your stand mixer with your dough hook attached, add flour, baker's dry milk, yeast, salt, sugar, egg, milk, and tangzhong. Mix on low until a shaggy dough forms.
Stop the mixer, cover the bowl for 10 minutes and allow the dough to rest.
After 10 minutes, one tbsp at a time, add softened butter. Let butter fully incorporate into the dough until adding the next. For me it generally takes about 5-7 minutes to add all the butter and for it to be mostly incorporated.
Knead dough on low until dough is very smooth and no longer sticking to the sides. The dough will be tacky but also smooth and very elastic, passing the windowpane test. Kneading time beyond the butter stage is usually about 15-20 minutes.
When dough is ready, place in a lightly greased bowl and cover. Allow dough to rise for 1.5-2.5 hours or until doubled in size. If your kitchen is cool, Find a warm spot like on a sunny window sill, or in the oven (the oven should be OFF) with the oven light on. Because this dough has a fair amount of sugar, it will rise a little slower.
Prepare a pan with parchment. I would recommend using a 9x9 pan to get the best texture on these.
Punch down the dough and remove it from bowl. Divide dough into 16 pieces. Weighing your dough before you begin dividing will give you the most uniform size buns, but it is not required.
For rolls: Take each piece of dough, holding it in your palm and fold the sides into the center, creating a ball shape. Pinch the bottom pieces together. Then place the dough ball seam side down on the counter. Cup your hand over the dough and use a circular motion to further round out and create tension in the dough.
Place dough ball seam side down into the prepared pan. Repeat with remaining pieces of dough, spacing out evenly.
Cover the pan and allow dough to rise again for about another 45 minutes-1 hour, or until dough has puffed significantly.
About 20 minutes (more or less depending on your oven) into the second proof, preheat your oven to 350°F.
When buns are ready, brush the tops with 1-2 tbsp of milk, then evenly sprinkle with the 2 tbsp of granulated sugar. Place on the middle rack of your oven and bake for about 18-22 minutes or until buns are golden brown. A thermometer inserted into the bread should read 190°F.
Remove the bread from the pan to a wire cooling rack within 5-10 minutes. Let bread cool at least 30 min before eating. Store in an airtight container and best enjoyed within 24 hours but will keep for 3-4 days. Enjoy!
