Creating this delightful Chicken Poblano Casserole involves several straightforward steps:

1. Preheat the Oven: Preheat your oven to 350°F (175°C).
2. Sauté the Peppers: In a skillet, add a teaspoon of oil, and sauté the diced poblano peppers over medium heat for about 5 minutes, or until they are tender.
3. Mix Ingredients: In a large bowl, combine the cooked chicken, sautéed peppers, corn, black beans, cooked rice, cheddar cheese, Monterey Jack cheese, salsa, sour cream, chili powder, cumin, and salt and pepper. Stir until fully combined.
4. Prepare Baking Dish: Grease a 9×13-inch baking dish with cooking spray or oil.
5. Transfer Mixture: Pour the chicken mixture into the greased baking dish, spreading it evenly.
6. Top with Cheese: If desired, sprinkle additional cheese on top for an extra cheesy crust.
7. Bake: Place the casserole in the preheated oven and bake for about 30-35 minutes, or until it is heated through and bubbly.
8. Cool Slightly: Remove from the oven and allow to cool for about 5 minutes before serving.
9. Garnish: Sprinkle with chopped cilantro if desired, just before serving.

Following these steps ensures you create a flavorful and comforting Chicken Poblano Casserole that your family and friends will love!