Preheat your oven to 375°F (190°C) and lightly grease a 9x13-inch baking dish with non-stick cooking spray. In a medium bowl, whisk together the green enchilada sauce, sour cream, diced green chiles, and ground cumin until smooth and combined.

Add the shredded chicken to the sauce mixture and stir gently until all the meat is evenly coated. Taste and season with a pinch of salt and black pepper if desired.

Spread a thin layer of the creamy green sauce over the bottom of the prepared baking dish. Layer half of the halved corn tortillas over the sauce, overlapping them slightly to cover the bottom completely.

Spread half of the creamy chicken mixture evenly over the tortilla layer, then sprinkle with 1 cup of the shredded Monterey Jack cheese. Repeat the layers with the remaining tortillas, chicken mixture, and cheese.

Bake uncovered for 25 to 30 minutes, or until the casserole is bubbling hot around the edges and the cheese on top is melted and lightly golden. Let the casserole rest for 10 minutes before slicing to allow the layers to set.

Garnish the top of the hot casserole with the chopped fresh cilantro just before slicing. Serve warm alongside Mexican rice, refried beans, or a crisp green salad.