Preheat your oven to 350°F (175°C).
In a large bowl, combine cream of chicken soup, sour cream, shredded cheddar cheese, dry onion soup mix, and milk. Mix well.
Season the chicken breasts with salt and pepper. Heat olive oil in a skillet over medium heat and brown the chicken breasts on both sides for about 5 minutes. They do not need to be fully cooked.
In the bottom of the 9x13 inch baking dish, spread the cooked rice evenly.
Place the browned chicken breasts on top of the rice in the baking dish.
Pour the creamy mixture over the chicken and rice, ensuring everything is well covered.
Cover the baking dish with aluminum foil and bake in the preheated oven for 30 minutes.
After 30 minutes, remove the foil and bake for an additional 15 minutes, until the chicken is cooked through and the sauce is bubbly.
Once done, let it cool slightly before serving.