Prepare the Chicken: Start with cooked chicken that you have already shredded into small pieces. Rotisserie chicken works great, or you can boil or bake chicken breasts until fully cooked. Shredding the chicken finely helps it spread evenly inside the tortillas, so every bite feels balanced and tender. Set the chicken aside while you work on the sauce.
Make the Roux: Place a saucepan over medium heat and melt the butter completely. Once the butter looks glossy, sprinkle in the flour and stir right away. Keep stirring for about one minute until the mixture looks smooth and lightly bubbly. This step builds the base for a creamy sauce without lumps.
Build the Sauce: Slowly pour the chicken broth into the saucepan while stirring constantly. The sauce will start thin, then gradually thicken as it heats. Add the green enchilada sauce and green chiles next. Stir well so everything blends together. Let it cook for a few minutes until the sauce looks smooth and slightly thickened.
Finish the Creamy Sauce: Lower the heat and gently stir in the sour cream. Keep stirring until the sauce turns creamy and uniform. Add the shredded mozzarella cheese and continue stirring until the cheese melts fully. The sauce should look rich and silky at this point. Remove it from heat so it does not overcook.
Assemble the Enchiladas: Preheat your oven to 375°F. Spread a thin layer of sauce on the bottom of a baking dish. Lay out the tortillas and fill each one with shredded chicken, a sprinkle of cheese, and a bit of parsley. Roll them up snugly and place them seam side down in the dish.
Add the Sauce: Pour the remaining white sauce evenly over the rolled tortillas. Use a spoon to spread it into all the corners so every enchilada gets coated. Sprinkle extra mozzarella cheese on top for a bubbly finish once baked.
Bake Until Bubbly: Place the dish in the oven and bake for about 25 to 30 minutes. The sauce should bubble gently and the cheese on top should melt and lightly brown. Let the enchiladas rest for a few minutes before serving so the sauce settles nicely.
