Set your oven to 375°F (190°C) and coat a 9×12-inch casserole dish with grease to prepare it.
Warm the olive oil in a skillet over medium heat, then add the chopped onion and a pinch of kosher salt; cook until softened, about 2-3 minutes.
Stir in the minced garlic, chili seasoning, and ground cumin; cook for an additional minute to bring out the spices’ aroma.
Mix in the shredded chicken until everything is combined well and then remove the skillet from the heat.
In a large mixing bowl, blend the green salsa and sour cream until smooth and creamy.
Spread ¾ cup of this salsa verde mixture evenly on the bottom of the casserole dish.
Place 8 tortilla halves over the sauce layer.
Distribute half of the chicken mixture evenly, then pour 1 cup of salsa verde sauce over it and sprinkle with ½ cup of grated Monterey Jack cheese.
Add another layer of 8 tortilla halves on top.
Top with the remaining chicken, followed by 1 more cup of salsa verde sauce and ½ cup of cheese.
Finish with the last 8 tortilla halves, spread the remaining salsa verde sauce on top, and cover with the rest of the cheese.
Bake the casserole in the preheated oven for 15 to 20 minutes until the cheese melts completely and bubbles around the edges.
Take the casserole out of the oven and let it rest for a few minutes before serving.
Garnish with sliced jalapenos, crumbled cotija cheese, diced red onion, and freshly chopped cilantro for extra flavor.
