In a mixing bowl, combine the shredded chicken, chipotle sauce, red onion, and cilantro. Mix thoroughly and season with salt and pepper to taste.
Heat a large skillet over medium heat and add 1 tablespoon of olive oil.
Place one tortilla in the skillet, and sprinkle half of the mozzarella and cheddar cheese evenly over it.
On one half of the tortilla, spoon a generous amount of the spicy chicken mixture.
Fold the other half of the tortilla over the filling, pressing gently to secure it. Cook for about 3-4 minutes until the bottom is golden and crispy, then carefully flip and cook the other side for another 3-4 minutes.
Remove the quesadilla from the skillet and let it cool for a minute before slicing into wedges.
Repeat the process with the remaining tortillas, chicken mixture, and cheese.
Serve warm with optional sour cream and guacamole on the side.
Notes
Adjust the chipotle sauce to your spice preference.