Preheat the oven to 375°F (190°C) and grease a 9x12-inch casserole dish.

In a large skillet, heat olive oil over medium heat. Add chopped onions and sauté for 5-7 minutes.

Stir in minced garlic, chili powder, and cumin, cooking for 1 additional minute.

Add shredded cooked chicken to the skillet, mixing until heated through.

In a separate bowl, mix salsa verde and sour cream until smooth.

Spread ¾ cup of salsa verde mixture at the bottom of the casserole dish.

Layer 8 corn tortilla halves over the salsa verde, followed by half of the chicken mixture, 1 cup of salsa verde, and ½ cup of cheese.

Repeat with another layer of tortilla halves, remaining chicken mixture, salsa verde, and cheese.

Top with a final layer of tortilla halves, remaining salsa verde, and cheese.

Bake for 15-20 minutes until cheese is melted and bubbling.

Let cool for 10-15 minutes before serving.