For pancakes: In a large bowl, stir together flour, salt, sugar, and five-spice powder (if using). Add ¾ cup (180 grams) water, and mix to form a shaggy dough. Knead until it forms a smooth ball, about 5 minutes. Cover with a damp cloth. Let stand for about 1 hour.

For sauce: In a small bowl, whisk together soy sauce, 2 tablespoons (30 grams) water, scallion, sugar, sesame seeds, and garlic (if using).

Divide dough in half (about 243 grams each). Roll half of dough into a 15x9-inch rectangle. (Keep remaining dough covered with damp cloth.) Make a 3-inch-long cut at 5 inches down one long side and then at 10 inches; repeat on opposite long side. Rub about 1½ teaspoons (7.5 grams) neutral oil all over surface of rectangle, and sprinkle with half of scallions, half of sesame seeds (if using), and half of salt.

With dough oriented vertically, starting at bottom, fold side flaps of dough over center piece. Fold that entire rectangle forward onto center level. Fold center side flaps over, and repeat. Roll into about a 7x5½-inch rectangle (about ¾ inch thick). (Take care not to roll too firmly, as you don’t want the dough layers to bind and you want to keep some small pockets of air between them.)

In a 10-inch saucepan, heat 2 tablespoons (28 grams) neutral oil over medium heat. Add pancake; cover and cook until golden brown, 3 to 5 minutes per side. Transfer to a cutting board, slice, and serve with sauce.

Repeat procedure with remaining dough, remaining 1½ teaspoons (7.5 grams) oil, remaining scallions, remaining salt, and remaining sesame seeds (if using). Add more oil as needed.