Morning or the Evening Before
In a medium bowl, whisk together the flour and baking powder, then drizzle in the 2 tablespoons vegetable oil and toss. Stir in about 1 cup (240 ml) water to make a soft dough. Transfer the dough to a work surface and knead until it’s smooth and elastic, about 5 minutes; it shouldn’t be stiff. If it’s difficult to knead, set it aside to rest for a few minutes before trying again. Cover with the overturned bowl and let the dough rest for 30 minutes.
Shape into a log and cut into twelve equal portions. Use a small rolling pin to roll each portion into a thin rectangle about 12 inches (30.5 cm) long. Brush lightly with sesame oil, sprinkle lightly with a pinch of salt and scallions, then roll up the rectangle from one long side to enclose the scallions. Shape the roll into a flat spiral and pinch the end to the spiral to secure it. Using the rolling pin, lightly floured, roll the spiral out as thin and flat as possible (the scallions will poke through the dough, and that’s fine), then set aside and repeat to make the remaining pancakes. Put them on a plate in a single layer, or with waxed paper between the layers, cover with plastic wrap, and refrigerate.
In a large skillet or sauté pan, heat about ⅛ inch (3 mm) vegetable oil over medium-high heat. When it shimmers, add two or three pancakes and cook until nicely browned on each side, 4 to 5 minutes total. Remove to paper towels to drain. Repeat with the remaining pancakes and more oil, if needed, then serve.