Place flour in a bowl. Add hot water slowly in a steady stream, mixing well after each addition. Add cold water; mix until no dry spots remain. Knead dough lightly by hand until a ball is formed. Place dough in an oiled resealable plastic bag; seal the bag and let dough rest for 30 minutes.
Place scallions in a bowl; season with salt and pepper.
Roll dough out onto a floured work surface into a thin rectangle using a rolling pin. Spread butter all over; sprinkle evenly with salt and pepper. Spread scallions over the dough, leaving top edge of the dough empty. Roll dough up carefully from the opposite edge, keeping scallions in place and pulling dough a little with every roll to make it tight.
Cut the roll into 3- to 4-inch-long pieces by hand; pinch and seal both ends. Lightly flatten each piece into a circular pancake.
Heat a nonstick saucepan with oil; cook pancakes until golden brown, about 3 minutes per side. Crush 2 sides of the pancakes with spoons or ladles until flaky.