How to Make It
In a small skillet, heat 1/2 teaspoon of the oil. Add the Serrano peppers and cook over medium-high heat until charred in spots and tender, about 5 minutes. Transfer the peppers to a cutting board to finely chop.
In a non-stick skillet, heat 1/2 teaspoon of the oil. Place one tortilla in the skillet. Scatter 1/2 cup cheddar cheese and half of the chopped Serrano chiles evenly over the top. Top it with the second tortilla and cook over moderately high heat until crisp on the bottom, about 3 minutes. Flip it over and cook for another 2-3 minutes until cheese is melted and the second side is golden. Repeat with the remaining oil and second quesadilla. Cut the quesadillas into wedges and serve.