01 - Preheat oven to 350°F (175°C). Lightly grease a 9x13-inch baking dish.
02 - In a mixing bowl, blend shredded chicken, Monterey Jack cheese, sour cream, green onions, garlic powder, ground cumin, salt, and black pepper until evenly incorporated.
03 - In a medium saucepan over medium heat, melt butter. Stir in flour and cook for 1 to 2 minutes, whisking until mixture bubbles but does not brown.
04 - Gradually whisk in chicken broth and cook, stirring constantly, until the sauce thickens slightly, approximately 3 minutes.
05 - Remove saucepan from heat. Whisk in sour cream, diced green chilies, onion powder, and salt until smooth and creamy.
06 - Distribute the chicken filling evenly among tortillas. Roll each tortilla tightly and arrange seam-side down in the prepared baking dish.
07 - Pour the white sauce evenly over the filled tortillas. Sprinkle remaining Monterey Jack cheese over the top.
08 - Bake uncovered for 25 to 30 minutes, or until the cheese is melted, sauce bubbles, and the top is lightly golden.
09 - Allow enchiladas to cool briefly. Garnish with chopped cilantro and extra green onions before serving.