Step 1

Add 2 cups flour and 1/2 teaspoon salt to a large mixing bowl and pour the boiling hot water all over the flour. Use a fork or a pair of chopsticks to stir and mix so that all the water is absorbed into the flour and the flour is damp. Pour the room temperature water all over the dough and knead the dough with your hands just until a dough is formed and there aren’t any visible dry flour lumps (be careful not to overknead). Cover the dough with plastic wrap and rest for a minimum of 30 minutes or refrigerated for up to 8 hours. If refrigerating, bring to room temperature before proceeding.

Step 2

Add two-thirds of the scallions to a heatproof bowl. Heat up the canola oil in a small pot over medium heat until just beginning to shimmer, 1 to 2 minutes, then add the scallion ends, cilantro stems and onion ends. Slowly raise the heat to medium-high and let steep until the scallions and onion ends are golden brown, about 3 minutes. Carefully strain and pour the hot oil over the scallions in the bowl.

Step 3

Divide the dough into 4 equal balls. Roll out 1 ball on a well-oiled flat surface as thin as possible into a large circle that is about 12 inches in diameter. Using a spoon, spread 1/4 cup scallion oil and 2 tablespoons sliced scallions and sprinkle with salt on the pancake, leaving a rim. Sprinkle a thin layer of dry flour evenly over the oiled pancake dough. Make 4 vertical cuts in the dough, two upper and two lower, leaving the center intact. Starting on the right side, fold the two vertical pieces on top of each other, then fold that section into the middle. Fold the middle two vertical sections over that dough, then roll it towards the center of the remaining section. Fold the last two sections over that dough, gathering the edges until the scallions are encased in the dough. Turn the dough seam-side down and roll into a 5- to 6-inch disc. Repeat with the remaining dough and filling, covering with plastic to keep from drying out.

Step 4

Place a large cast-iron skillet over medium heat. Lay the dough flat in the skillet and start cooking it without adding oil. Cook for 1 minute, then flip to the other side and cook for 1 more minute. Repeat the flipping a couple more times, cooking the pancake until both sides golden, 5 to 6 minutes. When the pancake starts to puff up a little in the middle and both sides are golden, add 1/2 tablespoon canola oil around the edges of the pancake to make the outer layer extra crispy. Cook for about 15 seconds on each side; the scallion pancake is ready. Repeat to cook the remaining pancakes.