01 - Preheat oven to 350°F (175°C) and grease a 9x13-inch baking dish.
02 - Combine shredded chicken, 1 cup Monterey Jack cheese, 1/2 cup sour cream, green onions, garlic powder, cumin, salt, and black pepper in a mixing bowl until thoroughly incorporated.
03 - Melt unsalted butter in a saucepan over medium heat. Add flour and whisk constantly for 1 to 2 minutes until mixture is bubbling but not browned.
04 - Slowly pour in chicken broth, whisking continuously. Cook for about 3 minutes, stirring, until sauce thickens slightly. Remove from heat and whisk in sour cream, diced green chilies, onion powder, and salt until smooth.
05 - Portion the chicken mixture evenly into each flour tortilla. Roll each tortilla snugly and place seam-side down in the prepared baking dish.
06 - Evenly pour white sauce over the assembled tortillas. Sprinkle remaining 1 cup Monterey Jack cheese on top.
07 - Bake, uncovered, for 25 to 30 minutes until the dish is bubbling and lightly golden on top.
08 - Allow enchiladas to cool briefly. Garnish with chopped cilantro and additional green onions before serving.