Process 2 cups flour and baking powder in a food processor. With motor running, add 2/3 cup cold water; process until dough forms (about 40 seconds).
Transfer to a plate and set aside. Add remaining flour and salt to food processor, and with motor running, add 2/3 cup boiling water; process until dough forms (about 30 seconds).
Return reserved dough to food processor. Pulse until both doughs come together (about 35 seconds). Transfer to a lightly floured work surface and knead until smooth (4 minutes). Transfer to a greased bowl, cover. Let sit at room temperature for 2 hours.
Halve dough. Using a rolling pin, roll 1 dough half into a 10 inch x 20 inch rectangle. Brush with 1 tbsp canola oil and half the sesame oil. Sprinkle with half the scallions, half the chile flakes, and half the white pepper.
Beginning with one long side, tightly roll dough like a jelly roll. Cut roll crosswise into 3 pieces, slightly stretch each piece and starting from one edge, coil piece horizontally tucking the end underneath.
Using your hand, gently flatten coil into a disk. Using a rolling pin, flatten into a 5 inch circle.
Repeat with remaining pieces and second dough half. Follow above instructions for the following ingredients: 1 tbsp canola oil, remaining sesame oil, scallions, chile flakes, and white pepper. Let pancakes sit for about 10 minutes.
Heat oven to 200 degrees F. Heat 2 tsp canola oil in a 10 inch nonstick skillet over medium heat. Add 1 pancake to skillet. Cook, swirling skillet and turning once, until golden and crisp (about 10 minutes).
Transfer to a baking sheet and place in oven to keep warm. Repeat with remaining oil and pancakes. Cut into wedges to serve.