01 - Preheat oven to 350°F (175°C). Lightly grease a 9x13-inch baking dish.
02 - In a bowl, combine shredded chicken, Monterey Jack cheese, sour cream, green onions, garlic powder, ground cumin, salt, and black pepper until thoroughly mixed.
03 - In a saucepan over medium heat, melt unsalted butter. Stir in all-purpose flour and cook for 1-2 minutes until bubbling but not browned.
04 - Gradually whisk in chicken broth and cook, stirring frequently, until slightly thickened, about 3 minutes. Remove from heat and whisk in sour cream, diced green chilies, onion powder, and salt until smooth.
05 - Evenly distribute the chicken filling among flour tortillas. Roll each tortilla and arrange seam-side down in the prepared baking dish.
06 - Pour white sauce evenly over the arranged tortillas. Sprinkle with remaining Monterey Jack cheese.
07 - Bake uncovered for 25 to 30 minutes, or until sauce is bubbling and the top is lightly golden.
08 - Allow dish to cool slightly. Garnish with chopped cilantro and extra sliced green onions before serving.