1. Heat the oven to 200 F.
  2. Put a wire rack on a baking sheet and set it in the middle of the oven.
  3. Put 1 tablespoon of the oil in a skillet over medium heat.
  4. When the oil is hot, put a tortilla in the skillet.
  5. Top with a quarter of the cheese, scallions, and chiles.
  6. Cook until the cheese begins to soften a bit and the tortilla turns golden, 3 to 5 minutes; then fold the tortilla in half.
  7. Flip and cook until the cheese is just melted and both sides are toasted, another minute or two.
  8. Transfer the quesadilla to the prepared baking sheet to keep warm.
  9. Repeat the process with the remaining tortillas and fillings, starting with heating the oil.
  10. Cut into wedges and serve with the salsa.