Preheat your oven to 375°F (190°C). Lightly grease a 9x13-inch baking dish with nonstick spray or butter and set aside.
In a large mixing bowl, stir together the cream of chicken soup, chicken broth, sour cream, garlic powder, onion powder, black pepper, and salt until smooth and well combined.
Add the shredded rotisserie chicken, cooked rice, and broccoli florets to the bowl. Stir gently until everything is evenly coated in the creamy sauce. Fold in 1 1/2 cups of the shredded cheddar cheese and stir to combine.
Assemble and Bake
Pour the mixture into the prepared baking dish and spread it into an even layer. Sprinkle the remaining 1/2 cup of shredded cheddar cheese evenly over the top.
If using the optional crunchy topping, stir together the panko breadcrumbs and melted butter in a small bowl until the crumbs are evenly moistened. Set aside — you will add this later.
Cover the baking dish tightly with aluminum foil and bake for 20 minutes, until the casserole is hot and beginning to bubble around the edges.
Remove the foil. If using the panko topping, sprinkle it evenly over the cheese now. Return the uncovered dish to the oven and bake for an additional 12-15 minutes, until the cheese is fully melted, golden, and bubbly and the breadcrumbs (if using) are lightly toasted.
Remove from the oven and let the casserole rest for 5 minutes before serving. Garnish with fresh chopped parsley if desired and serve hot.
Notes
Make-ahead: Assemble the casserole, cover tightly, and refrigerate up to 24 hours before baking. Add 10 extra minutes to the covered bake time if going straight from the fridge. Storage: Refrigerate leftovers in an airtight container for up to 4 days. Add a splash of chicken broth when reheating to keep the rice moist. Freeze: Cool completely, portion into freezer-safe containers, and freeze up to 3 months. Thaw overnight in the fridge before reheating. Rice tip: Pre-cooked, day-old, or microwavable pouch rice works best for consistent texture. If using raw rice, add an extra 1/2 cup broth and extend covered bake time to 45 minutes. Cheese tip: Always shred your own cheddar from a block — pre-shredded cheese contains anti-caking agents that prevent it from melting as smoothly.