Step 1: Preheat the Oven

• Preheat your oven to 350°F (175°C).
• Lightly spray a 9×13-inch baking dish with cooking spray.

Step 2: Make the Enchilada Sauce

1. Heat olive oil in a large skillet over medium heat. Add diced onion and kosher salt. Sauté for 5 minutes until translucent.
2. Stir in chili powder and cumin, cooking for 30 seconds until aromatic.
3. Add flour and stir continuously to avoid lumps. Slowly whisk in chicken stock.
4. Stir in tomato sauce and garlic. Simmer for 5 minutes, stirring occasionally. Blend for a smoother texture, if desired.

Step 3: Prepare the Filling

1. In a large bowl, combine shredded chicken, kosher salt, black pepper, diced green chiles, and drained black beans.
2. Stir in ½ cup of enchilada sauce to coat evenly.

Step 4: Assemble the Casserole

1. Dip 6 corn tortillas into the enchilada sauce, coating both sides. Layer them on the bottom of the baking dish.
2. Spread half of the chicken mixture over the tortillas.
3. Sprinkle 1 cup of shredded cheese on top.
4. Repeat the layers with the remaining tortillas, chicken mixture, and cheese. Pour any leftover enchilada sauce over the top layer and finish with 2 cups of cheese.

Step 5: Bake

1. Place the casserole in the preheated oven.
2. Bake uncovered for 25 minutes, or until the cheese is melted, bubbly, and golden brown.
3. Let cool for 5 minutes before slicing and serving.