Preheat Oven (Optional): If you prefer a baked finish, preheat your oven to 375°F (190°C).
Sauté Onion and Chicken: In a large oven-safe skillet, heat the olive oil over medium heat. Add the chopped onion and sauté until translucent, about 3-4 minutes. Add the chicken pieces, season with salt and pepper, and cook until the chicken is no longer pink, approximately 5-6 minutes.
Add Garlic: Stir in the minced garlic and cook for an additional 30 seconds until fragrant.
Add Rice and Liquids: Add the uncooked rice, condensed cream of chicken soup, and chicken broth to the skillet. Stir well to combine. Bring the mixture to a boil, then reduce the heat to low, cover, and let it simmer for about 15 minutes, or until the rice is cooked and has absorbed most of the liquid. Stir occasionally to prevent sticking.
Add Broccoli: Once the rice is tender, stir in the broccoli florets. If using fresh broccoli, cook for an additional 3-4 minutes until the broccoli is tender-crisp. If using frozen broccoli, cook until heated through.
Add Cheese: Stir in half of the shredded cheddar cheese until melted and well combined.
Optional Baking Step: If you prefer a baked casserole with a cheesy crust, sprinkle the remaining cheddar cheese on top and transfer the skillet to the preheated oven. Bake for 5-7 minutes, or until the cheese is melted and bubbly.
Garnish and Serve: Remove from heat (or oven) and let it sit for a few minutes before serving. Garnish with chopped fresh parsley if desired.