Position racks in the upper and lower thirds of the oven and preheat to 450 degrees F. Line 2 rimmed baking sheets with foil, then divide the fries between them. Bake, tossing once or twice, until crisp and golden brown, 30 to 45 minutes. Transfer to a large bowl.
Place the chiles in a bowl, cover with a plate and shake to release the seeds. Fish out the chiles, leaving the seeds behind.
Heat the vegetable oil in a large skillet over medium heat. Add the cumin seeds, peppercorns, chopped chiles and 1 teaspoon salt and cook, stirring, until toasted, 2 to 3 minutes. Stir in the scallions and remove from the heat.
Toss the fries with the spiced oil and season with salt. Remove and discard any large chile pieces.
Photograph by Con Poulos
Recipe courtesy of Food Network Magazine