01 - Preheat oven to 350°F (175°C). Lightly grease a 9x13-inch baking dish and set aside.
02 - In a large bowl, mix shredded chicken, 1 cup shredded Monterey Jack cheese, 1/2 cup sour cream, green onions, garlic powder, cumin, salt, and black pepper until well combined.
03 - In a medium saucepan over medium heat, melt butter. Stir in flour and cook, whisking constantly, for 1 to 2 minutes until bubbling but not browned.
04 - Gradually whisk in chicken broth and continue stirring until the mixture is slightly thickened, about 3 minutes. Remove from heat and whisk in 1 cup sour cream, green chilies, onion powder, and salt until the sauce is smooth.
05 - Divide the chicken filling evenly among the tortillas. Roll each tortilla tightly and place seam-side down in the prepared baking dish.
06 - Pour the white sauce evenly over the filled tortillas. Sprinkle with the remaining 1 cup Monterey Jack cheese. Bake uncovered for 25 to 30 minutes, until sauce is bubbling and cheese is lightly golden.
07 - Remove baking dish from the oven and let cool briefly. Garnish enchiladas with chopped cilantro and extra green onions before serving.