Preheat your oven to 350°F (175°C). Lightly grease a 9x13-inch casserole dish with butter or nonstick cooking spray.

In a large mixing bowl, whisk together the cream of mushroom soup, milk, water, and onion soup mix until smooth and well combined. The mixture should look slightly thick and creamy.

Spread the rinsed uncooked rice evenly across the bottom of the greased casserole dish. Pour the soup mixture slowly over the rice, making sure every grain is coated. Gently shake the dish or tap it on the counter to help the liquid settle evenly.

Place the chicken breasts on top of the rice mixture, pressing them down slightly so they are partially submerged. Sprinkle paprika, salt, and black pepper evenly over the chicken.

Cover the dish tightly with aluminum foil. Bake for 45 minutes.

After 45 minutes, carefully remove the foil. Check that the rice is tender and most of the liquid has been absorbed. Sprinkle the shredded cheddar cheese evenly over the top. Return the dish to the oven uncovered and bake for another 15 minutes, until the cheese is melted, bubbly, and lightly golden.

Remove from the oven and let the casserole rest for 5 to 10 minutes before serving. Garnish with fresh parsley and serve hot.