01 - Preheat oven to 350°F (175°C) and grease a 9x13-inch baking dish.
02 - In a large bowl, combine shredded chicken, 1 cup Monterey Jack cheese, 1/2 cup sour cream, green onions, garlic powder, cumin, 1/4 teaspoon salt, and black pepper until evenly incorporated.
03 - In a saucepan over medium heat, melt butter. Stir in flour and cook for 1 to 2 minutes, stirring constantly, until mixture is bubbling but not browned.
04 - Gradually whisk in chicken broth and cook, stirring frequently, for approximately 3 minutes until slightly thickened. Remove from heat and whisk in 1 cup sour cream, diced green chilies, onion powder, and 1/2 teaspoon salt until sauce is smooth.
05 - Distribute chicken filling evenly among the flour tortillas. Roll each tortilla tightly and place seam-side down in the prepared baking dish.
06 - Evenly pour the white sauce 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 the top is lightly golden.
07 - Allow the enchiladas to cool briefly. Garnish with chopped cilantro and extra sliced green onions before serving.