In a small pot, combine 1/2 cup water and 1/4 cup flour. Cook on medium heat, use a whisk to stir continuously until the liquid is absorbed and the flour mixture looks like mashed potatoes (approximately 4 to 4.5 minutes). Set aside to cool.

Microwave the milk for 15-20 seconds until warm (or warm it up whatever way you typically do, the milk temperature needs to be approximately 105-115°F). Pour the milk into a mixing bowl of a stand mixer, add the yeast and sugar and use the whisk from step 1 to mix until the sugar is dissloved and the yeast is not clumpy. Check that the yeast is active by waiting 5-10 minutes to see if the yeast mixture is slightly bubbly or foamy.

Add 2 cups flour, 2 tablespoons olive oil, and salt to the mixing bowl. Use a spatula to scrape all of the tangzhong into the mixing bowl. Use a dough hook to mix at lowest speed for 1 minute. If the dough seems dry, add any extra drops of oil or milk in your measuring cups/spoons. Stop the mixer, scrape the sides of the bowl down, and continue mixing at low speed for 10 more minutes. Resist the urge to add more flour.

Oil a 4 cup (or medium sized) bowl with a few drops of olive oil. Scrape the dough off the dough hook, scrape the sides of the bowl, and transfer the dough into the oiled bowl. Use a spatula to turn the dough over a few times to coat both sides with oil and cover the dough with plastic wrap and a dry dish towel. Allow the dough to rise in a warm, draft-proof place to rise (such as in a cold oven, near the oven light turned on) for 1 hour for the yeast to double (might be ready in 45 minutes if you are in a hurry). Allow about 25 minutes total to prepare the dough to rise.

While the dough is rising, line a square baking pan (8x8) with parchment paper, set aside. Fine chop the scallions (1/4 inch or smaller) and transfer to a bowl. Add the remaining oil and salt (if using), stir to combine, and set aside.

After 1 hour, the dough should doubled in size, transfer it to a lightly floured work surface (save the plastic wrap to reuse later). Stretch or use a rolling pin to shape the dough into a 11 x 16 inch rectangle, approximately 1/4 inch thick. Spread about 3/4 of the scallion oil mixture on the dough and then roll the dough up along the long side so that you end up with a long skinny log instead of a short wide one.

Cut the log into 9 pieces, dip one end of the roll in the bowl of scallion oil, and place them dipped side up in the parchment paper lined pan in a 3x3 grid. Spread the remaining scallions and oil on top of the rolls, cover with the plastic wrap and dish towel and return to the warm, draft-proof place for a second rise for 25 minutes.

Take the proofed, unbaked rolls out of the oven, allow them to continue to proof while preheating oven at 350°F (check that a middle rack is in place). When the oven is hot, remove the towel and plastic wrap, and bake for 30-35 minutes until the bread is golden brown. Cool the bread in the pan on a cooling rack and serve when cool to touch. When cooled to room temperature, store leftover bread in an airtight covered container for freshness.