Preheat oven to 400 degrees and prepare a 9x13 casserole dish with non-stick spray.
Spread the chicken evenly along the bottom of the casserole dish.
Pour the rice on top of the chicken.
Add frozen peas and carrots and chopped onion on top of the rice.
In a large bowl, mix the soup, chicken broth, paprika, poultry seasoning, salt, and pepper until well combined. Spread the mixture on top of the peas and carrots.
Top with the sliced butter.
Cover with foil and bake for 1 hour. Test to see if the rice is cooked. If not, uncover and cook for an additional 30 minutes or so.