
This cheesy loaded Mexican chicken casserole—filled with a creamy sauce, two kinds of cheese, and plenty of chicken—has something for everyone.
Preheat oven to 350°. Grease a 13"-by-9" pan with cooking spray.
In a large skillet over medium heat, heat oil. Cook onion, stirring occasionally, until slightly tender and just turning golden, about 5 minutes. Add jalapeño (if using) and garlic and cook, stirring, until fragrant, about 1 minute more. Add chicken, beans, corn, salt, chili powder, cumin, and pepper and cook, stirring occasionally, until warmed through, about 5 minutes. Add tomatoes and soup and stir to combine.
Spread half of chicken mixture on bottom of prepared pan. Top with half of chips, half of cheddar, and half of Monterey Jack. Repeat with remaining chicken mixture, chips, cheddar, and Monetery Jack.
Bake casserole until bubbly and cheese is melted, 25 to 30 minutes.
Top with cilantro, tomatoes, avocado, and jalapeño.