Preheat your oven to 350°F (175°C).
In a large skillet, heat the olive oil over medium heat. Add the diced onion and minced garlic. Sauté for about 5 minutes, or until the onion is translucent.
In a mixing bowl, combine the cooked chicken, rice, chicken broth, cream of mushroom soup, frozen vegetables, salt, pepper, and paprika. Stir until all ingredients are well combined.
Add the sautéed onion and garlic to the mixture and stir gently.
Transfer the mixture into a greased 9x13-inch baking dish, spreading it evenly.
Cover the baking dish with aluminum foil to prevent drying out, and bake in the preheated oven for 30 minutes.
After 30 minutes, remove the foil, sprinkle the shredded cheddar cheese over the top, and return to the oven. Bake for an additional 15 minutes, or until the cheese is melted and bubbly.
Once done, let the casserole sit for a few minutes before serving.