Preheat oven to 375°F. Grease a 9x13-inch or similar casserole dish.

In a small bowl, combine all of the ingredients to make the fajita seasoning.

Heat a skillet (I like to use cast iron) over medium high heat. Add 1 tablespoon of the olive oil.

Sprinkle the chicken with half of the fajita seasoning and add to the skillet. Cook until browned an completely cooked through, about 4-5 minutes. Remove from skillet and set aside.

Add remaining tablespoon of the olive oil to the skillet. Add onion and peppers and sprinkle with remaining fajita seasoning. Cook until vegetables are softened and start to caramelize, about 5-6 minutes. Combine with the chicken.

Whisk together the enchilada sauce, sour cream, and milk. Pour enough mixture into the prepared baking dish to cover the bottom generously.

Spoon chicken fajita mixture into the flour tortillas, roll up, and place seam side-down in the dish.

Pour remaining enchilada sauce mixture over the top of the tortillas and sprinkle with mozzarella cheese.

Cover with foil and bake for 20 minutes. Remove foil and bake until sauce bubbles and cheese just begins to turn brown, about 10 minutes more.

Serve enchiladas with chopped avocados and cilantro, or as desired.