Heat oil in a large skillet over medium-high heat. Add chicken and cook until browned, about 5 minutes. Add onion and garlic and cook until softened, about 5 minutes.
Stir in tomatoes, chiles, chili powder, cumin, and salt and pepper. Simmer for 5 minutes.
Spread 1/2 of the chicken mixture into a 9x13-inch baking dish. Sprinkle with 1/2 of the cheese. Top with remaining chicken mixture and sprinkle with remaining cheese.
Bake for 20 minutes. Remove from oven and top with sour cream and cilantro. Return to oven and bake for an additional 5 minutes.
Interesting Facts
This casserole can be made ahead of time and stored in the refrigerator for up to 3 days.
This is a great way to use up leftover cooked chicken.
This casserole can also be frozen and reheated for a quick meal.