01 - Preheat oven to 350°F (175°C). Lightly grease a 9x13-inch baking dish.
02 - In a mixing bowl, blend shredded chicken, 1 cup Monterey Jack cheese, 1/2 cup sour cream, green onions, garlic powder, cumin, salt, and black pepper until the mixture is uniform.
03 - In a saucepan, melt butter over medium heat. Stir in flour and cook for 1 to 2 minutes, whisking constantly, until mixture is bubbling without browning.
04 - Gradually pour in chicken broth, whisking steadily, and cook for about 3 minutes until slightly thickened.
05 - Remove saucepan from heat. Whisk in sour cream, diced green chilies, onion powder, and salt until sauce is smooth and well combined.
06 - Evenly distribute chicken filling among flour tortillas, roll up tightly, and arrange seam-side down in the prepared baking dish.
07 - Pour white sauce evenly over arranged enchiladas and top with remaining shredded Monterey Jack cheese.
08 - Transfer the dish to the oven and bake uncovered for 25 to 30 minutes, or until the surface is lightly golden and the sauce is bubbling.
09 - Allow to cool briefly. Garnish with chopped cilantro and extra green onions before serving.