Preheat the oven: Set your oven to 375°F (190°C). Lightly oil a 9x13-inch baking dish.
Warm the tortillas: Wrap tortillas in foil and warm in the oven for 5–7 minutes, or microwave under a damp paper towel for 30–45 seconds.
Warm tortillas roll without tearing.
Make the roux: In a medium saucepan over medium heat, melt the butter. Whisk in the flour and cook for 1 minute until foamy and lightly golden.
Build the sauce: Slowly whisk in the chicken broth until smooth. Simmer 2–3 minutes until slightly thickened.
Reduce heat to low and whisk in sour cream, green chiles, cumin, chili powder, garlic powder, onion powder, salt, and pepper. Heat gently until just steamy. Do not boil.
Season to taste: Stir in lime juice.
Adjust salt and pepper as needed. You’re looking for a creamy, lightly tangy sauce with mild heat.
Mix the filling: In a bowl, combine shredded chicken, half the cheese, and diced onion (if using). Add 1/2 cup of the warm sauce and toss to coat.
This keeps the filling juicy.
Sauce the pan: Spoon 1/2–3/4 cup of sauce into the baking dish and spread to coat the bottom.
Fill and roll: Place a warm tortilla on a board. Add about 1/3 cup of the chicken mixture down the center. Roll snugly and place seam-side down in the dish.
Repeat with remaining tortillas.
Top with sauce and cheese: Pour the remaining sauce evenly over the enchiladas. Sprinkle the rest of the cheese on top.
Bake: Bake uncovered for 18–22 minutes, or until the cheese is melted and the sauce is bubbling at the edges. For extra browning, broil for 1–2 minutes at the end.
Finish and serve: Let rest for 5 minutes.
Garnish with chopped cilantro. Serve with lime wedges, sliced avocado, or a simple green salad.