In a large mixing bowl, combine the shredded chicken, black beans, corn, diced tomatoes with green chilies, cooked rice, taco seasoning, and half of the shredded cheddar cheese. Mix well until all ingredients are evenly combined. Season with salt and pepper to taste.
In a 9x13 inch casserole dish, spread a thin layer of salsa on the bottom to prevent sticking.
Lay three whole wheat tortillas over the salsa, allowing them to overlap slightly.
Spoon half of the chicken and bean mixture evenly over the tortillas.
Add another layer by placing three more tortillas over the filling, followed by the remaining chicken and bean mixture.
Top with salsa and sprinkle the remaining shredded cheddar cheese over the entire casserole.
Cover the casserole with aluminum foil and bake in the preheated oven for 25 minutes.
Remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and golden.
Allow the casserole to cool for a few minutes before serving. Drizzle sour cream over individual portions and garnish with chopped cilantro if desired.