01 - Preheat oven to 350°F (175°C). Lightly grease a 9x13-inch baking dish.
02 - In a mixing bowl, combine shredded chicken, 1 cup Monterey Jack cheese, 1/2 cup sour cream, green onions, garlic powder, cumin, salt, and pepper until thoroughly mixed.
03 - Melt unsalted butter in a saucepan over medium heat. Add flour, stirring constantly for 1 to 2 minutes, until the mixture is bubbling without browning.
04 - Gradually whisk in chicken broth. Continue stirring until the sauce thickens slightly, about 3 minutes. Remove saucepan from heat and whisk in sour cream, diced green chilies, onion powder, and salt until the sauce is smooth.
05 - Distribute the chicken filling evenly among the flour tortillas. Roll each and arrange seam-side down in the prepared baking dish.
06 - Pour the white sauce evenly over the assembled enchiladas. Sprinkle the remaining Monterey Jack cheese over the top.
07 - Bake uncovered for 25 to 30 minutes, until the sauce is bubbling and the cheese is golden at the edges.
08 - Let the enchiladas cool for several minutes. Garnish with chopped cilantro and additional green onions before serving.