Preheat your oven to 350 degrees F. Spray a 9-inch x 9-inch baking dish with non-stick cooking spray. Set aside.
If using 1 large breast, cut it in half to create two thin chicken breast pieces. Butterfly the chicken and then finish cutting all the way through.
Place a large skillet over medium heat. Cook chicken for 3 to 4 minutes per side, until no longer pink and cooked through.
Remove the chicken to a cutting board and finely chop or shred the chicken.
In a large bowl, stir together the cooked rice, sour cream, soup, and green chiles. Add the chicken, salt, and pepper and mix to combine.
Pour half of the rice mixture into your prepared dish and spread it into an even layer. Top with 1 cup of cheese. Pour the remaining rice mixture over the cheese, spread evenly, and then top with remaining cheese.
Bake for 40 to 45 minutes until the casserole is bubbly.
Remove from oven and allow to cool for 5 to 10 minutes. Serve warm.
I have made this casserole with uncooked white rice instead of instant rice. The rice is a little on the crunchy side at the end of the 45 minute cooking time. This recipe needs pre-cooked rice. Instant rice (1 cup uncooked and then prepared) or leftover cooked rice (2 cups cooked) from the night before are the best options.
You can substitute cream of chicken or cream of mushroom soup if needed.
To save on prep you can use a rotisserie chicken and chop or shred both breasts.