Preheat oven to 375°F (190°C). Lightly grease a 9×13-inch baking dish.
In a skillet, heat olive oil. Add onion and cook until soft. Stir in chiles, cumin, garlic, and chicken.
Combine sour cream and green enchilada sauce in a bowl until smooth.
Spread sauce, tortillas, chicken, and cheese in layers. Repeat until all ingredients are used, ending with cheese.
Bake uncovered for 25–30 minutes until bubbly and golden brown.
Top with cilantro and rest for 5 minutes before serving.
