01 - Preheat oven to 350°F (175°C). Lightly grease a 9x13-inch baking dish.
02 - Combine shredded chicken, 1 cup Monterey Jack cheese, 1/2 cup sour cream, sliced green onions, garlic powder, ground cumin, salt, and black pepper in a mixing bowl. Mix thoroughly until well blended.
03 - Melt unsalted butter in a saucepan over medium heat. Stir in all-purpose flour and cook for 1 to 2 minutes, whisking constantly, until bubbling but not browned.
04 - Gradually add chicken broth, whisking continuously. Cook for about 3 minutes, stirring, until the mixture is slightly thickened. Remove from heat and whisk in sour cream, diced green chilies, onion powder, and salt until the sauce is smooth.
05 - Divide the chicken filling evenly among the flour tortillas. Roll each filled tortilla and arrange seam-side down in the prepared baking dish.
06 - Pour the white sauce evenly over the filled tortillas. Sprinkle the remaining 1 cup Monterey Jack cheese over the top.
07 - Bake uncovered for 25 to 30 minutes until the enchiladas are bubbly and lightly golden on the edges.
08 - Allow the dish to cool slightly. Garnish with chopped cilantro and extra green onions just before serving.