Preheat the oven to 375°F. Grease a 9x12-inch casserole dish and set aside.
Heat the olive oil in a large skillet over medium heat. Add the onion and salt, cooking until softened. Stir in garlic, chili powder, and cumin, and cook for another minute.
Stir in the chicken until well incorporated. Remove from heat.
In a large bowl, combine salsa Verde and sour cream. Mix until smooth.
Layer ¾ cup of the salsa mixture on the bottom of the casserole dish. Top with 8 tortilla halves.
Add half of the chicken mixture, 1 cup of salsa Verde, and ½ cup cheese.
Repeat with another layer of tortillas, the remaining chicken, another cup of salsa Verde, and another ½ cup cheese.
Finish with a final layer of tortillas, the remaining salsa Verde, and the remaining cheese.
Bake for 15-20 minutes until the cheese is melted and bubbly. Add optional toppings and serve.