Preheat oven: Preheat your oven to 350°F and lightly grease a 9x13-inch casserole dish.
Prepare tortillas: In a large pan, heat a small amount of avocado oil. Lightly fry the corn tortillas for 1-2 minutes per side to prevent them from becoming soggy in the casserole. Set aside.
Cook vegetables: In the same pan, add diced bell peppers, onion, jalapeños, and mushrooms. Season with the listed seasonings and cook for 4-5 minutes, until softened. Add the minced garlic during the last minute and cook for 1 more minute.
Combine filling: Stir in chicken broth, diced tomatoes with green chilies, cream of chicken soup, and shredded rotisserie chicken. Mix well, then remove from heat.
Assemble casserole:
o Spread ½ cup of the chicken mixture on the bottom of the casserole dish.
o Add a layer of fried corn tortillas.
o Spread half of the remaining chicken mixture over the tortillas.
o Sprinkle 1 cup each of cheddar and Monterey Jack cheese on top.
o Repeat with another layer of tortillas, the remaining chicken mixture, and another 1 cup each of cheddar and Monterey Jack cheese.
Top with jalapeños: Arrange sliced jalapeños on top, placing them where each serving would be.
Bake: Place the casserole in the oven and bake for 25-30 minutes, or until the cheese is melted and bubbly.
Serve: Let the casserole rest for a few minutes before serving. Enjoy!