01 - Rub both sides of the chicken breasts evenly with taco seasoning to coat.
02 - Heat the vegetable oil in a large skillet over medium-high heat. Cook chicken breasts for 4 to 5 minutes per side, until the surface is golden and the internal temperature reaches 165°F. Remove from skillet.
03 - Transfer cooked chicken to a cutting board. Allow it to rest briefly, then chop into small bite-sized pieces.
04 - In a mixing bowl, combine the chopped chicken, grated cheese, corn, scallions, and cilantro. Toss gently to mix.
05 - Lay one tortilla flat. Spread one quarter of the filling evenly over half of the tortilla, leaving a 1/2-inch border. Fold the tortilla over to enclose the filling; repeat this process with the remaining tortillas and filling.
06 - Melt 2 tablespoons of butter in a 12-inch nonstick skillet over medium heat. Place 2 assembled quesadillas in the skillet and cook for about 2 minutes per side, pressing gently with a spatula, until the exterior is golden brown and cheese is melted.
07 - Melt the remaining 2 tablespoons of butter and cook the last 2 quesadillas as described above.
08 - Transfer quesadillas to a cutting board. Cut each into wedges and serve hot with sour cream, salsa, and guacamole if desired.