OPTION 1 - USING YOUR HANDS: Combine the flour and salt in a big bowl. Stir to mix well. Slowly drizzle in the hot water while mixing it with a pair of chopsticks (or a fork), until the water is fully absorbed. Slowly drizzle in the cool water, continuing to stir until many dough flakes form. Press the dough together, and try to combine the wet dough with the dry flour. Drizzle in a little extra water if there is any dry flour remaining. Knead until a firm ball is formed, about 5 minutes. Cover and let rest for 20 minutes.
OPTION 2 - USING A MIXER: Combine the flour and salt in the mixer bowl with the dough hook attachment. Turn it to the mix setting and slowly drizzle in the hot water followed by the cool water. After a minute of mixing, drizzling in a little extra water if there is any dry flour remaining. Turn to setting 4 and knead until a ball of dough is formed, about 3 minutes. Cover and let rest for 20 minutes.
Make the filling
While the dough is resting, combine the flour, oil, and salt in a small bowl. Mix until a smooth paste is formed.
If making the dipping sauce, combine all the ingredients with 1 tablespoon of water in a small bowl and mix until the sugar is dissolved.
Form the scallion pancakes
When the dough is done resting, knead for another minute until it is smooth. Cut the dough into 6 even pieces, about 76 grams per piece. Form the dough into balls using your hands.
Work on one dough ball at a time, covering the rest with plastic wrap to prevent drying out. Roll each dough ball into a thin rectangle with a rolling pin, aiming for around 6x10” (15x25 cm). Lift and turn the dough regularly as you roll it to prevent sticking. Spoon about 1 tablespoon of the filling onto the dough and spread it evenly with the back of a spoon, leaving about 1” (2.5 cm) on top and the left end without the filling. Sprinkle 2 heaping tablespoons of green onions onto the paste, concentrating most of it towards one side of the length and one side of the width, creating a loose L shape (see the blog post above for the step-by-step pictures).
Begin rolling the dough from the longer side of the dough where the green onions are concentrated, until you have one long tube. Lightly flatten the tube using your hand. Pinch the side with more green onion to seal it. Take the sealed side and gently pull and roll it towards the unsealed side, using your hand to smooth out the dough to push any large air bubbles out. Tuck the loose end under the rolled bun. Gently press down on the round disk with your hand to seal the pancake.
Set the formed pancake aside and cover it with plastic wrap. Repeat steps 4 and 5 until each pancake is ready.
Roll out the pancake
Roll each prepared pancake into a circle, about 7-8” (17-20 cm) wide. Flip and move it as you do to prevent sticking. Don’t worry if air bubbles burst through or some green onions fall out.
If you plan to store the pancakes and cook them later, place each pancake onto a piece of parchment paper and stack them. Transfer the pancakes to a large ziplock bag, squeeze out as much air as possible, and seal the bag. You can freeze the pancakes for up to 3 months.
Cook the pancakes
Heat a 9” (23 cm) cast iron pan (or a nonstick skillet) over medium-high heat and add enough oil to fully coat the bottom. Once the oil is hot, add a pancake. Use a pair of chopsticks (or a spatula) to swirl the pancake around to spread the oil and prevent sticking, for a few seconds. Cover the pan and turn the heat down to medium. Let the pancake cook, covered, for 1 minute. Remove the lid and flip the pancake, cover, and cook for another minute. Remove the lid. Use a spatula to press the pancake, to ensure even browning. Continue to cook, flipping regularly, until both sides are crisp and browned, about 3 minutes. Turn to medium-low heat if the pan gets too hot. Transfer the pancake to a cooling rack or a cutting board to cool. Repeat to cook all the pancakes you plan to serve.
Once the pancakes are slightly cooled enough to handle, cut into 6 pieces and transfer to a serving platter. Serve hot with the dipping sauce as an appetizer.
Cook frozen pancakes
Let the frozen pancakes thaw for 10 minutes then proceed from step 8.
Store and reheat cooked pancakes
Place the leftover pancakes in a ziplock bag by stacking them together. Store in the fridge up to 3 days. To reheat, add a pancake to a pan and heat over medium heat, cook, flip occasionally until the pancakes turn warm throughout.