01 - Preheat oven to 350°F (175°C) and lightly grease a 9x13-inch baking dish.
02 - In a mixing bowl, blend shredded chicken, Monterey Jack cheese, sour cream, green onions, garlic powder, cumin, salt, and black pepper until evenly mixed.
03 - Melt unsalted butter in a saucepan over medium heat, stir in all-purpose flour, and cook for 1 to 2 minutes, stirring, until bubbling but not browned.
04 - Slowly whisk in chicken broth to the saucepan. Continue stirring and cook until slightly thickened, about 3 minutes.
05 - Remove saucepan from heat and whisk in sour cream, diced green chilies, onion powder, and salt until the mixture is smooth.
06 - Evenly distribute the chicken mixture onto the center of each flour tortilla. Roll up tortillas and arrange seam-side down in the prepared baking dish.
07 - Pour the white sauce evenly over the filled tortillas. Sprinkle with the remaining Monterey Jack cheese.
08 - Bake uncovered for 25 to 30 minutes until the sauce is bubbly and the top is lightly golden.
09 - Allow enchiladas to cool slightly, then garnish with chopped cilantro and additional green onions before serving.