Adjust oven rack to middle position and heat oven to 450 degrees. Grease a 9-inch pie plate. Press the tortilla into the prepared pie plate and spray lightly with cooking spray.
Toss the chicken, cilantro, jalapeños (if using), 1 cup of cheese, ½ teaspoon of salt, and ½ teaspoon of pepper in a large bowl until combined. Spread the filling evenly over the tortilla.
In a separate bowl, whisk together the eggs, milk, flour, baking powder, and ½ teaspoon of salt until smooth. Slowly pour this mixture over the filling.
Bake until the surface is golden brown, about 20 to 25 minutes, and when a knife inserted into the center comes out clean.
Sprinkle the remaining 1 cup of cheese on top and bake for an additional 3 to 5 minutes, or until the cheese melts. Let it cool for 5 minutes before cutting into wedges.
Serve warm topped with sour cream, salsa, and guacamole if desired.
