In a large bowl, whisk together flour and salt. Gradually add the boiling water, stirring with chopsticks until a shaggy dough forms. Add the cold water and knead for 5-7 minutes on a lightly floured surface until the dough is smooth and elastic. Cover the dough with a damp cloth and let it rest for 30 minutes.

Divide the rested dough into 4 equal pieces. Take one piece and, on a lightly floured surface, roll it out into a thin rectangle (approximately 8x12 inches).

Brush the entire surface of the rolled-out dough with a thin layer of vegetable oil and sprinkle generously with about 1/4 cup of the chopped scallions.

Roll the dough tightly from one long side to the other, creating a log. Then, coil this log into a tight spiral shape, tucking the end underneath.

Gently flatten the spiral with your palm, then use a rolling pin to roll it out into a flat, round pancake about 6-8 inches in diameter. Repeat this process with the remaining dough pieces.

Heat 1-2 tablespoons of vegetable oil in a large skillet or frying pan over medium heat. Once hot, carefully place one or two pancakes (depending on pan size) in the skillet.

Fry the pancakes for 3-5 minutes per side, or until they are golden brown, crispy, and cooked through. Add more oil as needed between batches.

Remove the cooked pancakes and place them on a paper towel-lined plate to drain any excess oil. Serve immediately while hot.