I’m keeping it low-key, but this casserole has me smitten.

2 cups cooked chicken, shredded
1 can (10 oz) green enchilada sauce
1 can (4 oz) diced green chiles
1 cup sour cream
2 cups shredded cheddar cheese
1 cup shredded Monterey Jack cheese
12 corn tortillas
1/2 cup chopped onion
1 tablespoon olive oil
Salt and pepper to taste
Chopped fresh cilantro for garnish (optional)