Preheat your oven to 375°F (190°C). Lightly grease a 9x13 inch casserole dish.

If you haven't already, cook the rice according to package directions. You will need 3 cups of cooked rice.

Heat the olive oil in a large skillet over medium-high heat. Season the cubed chicken with a pinch of salt and pepper. Add the chicken to the skillet and cook until lightly browned and cooked through, about 5-7 minutes. Remove the chicken from the skillet and set aside.

In the same skillet, add the chopped onion and cook until softened, about 3-4 minutes. Add the minced garlic and cook for another minute until fragrant.

In a separate medium saucepan, melt 4 tbsp of butter over medium heat. Whisk in the flour and cook for 1 minute, stirring constantly to form a roux.

Gradually pour in the milk and chicken broth while whisking continuously to prevent lumps. Continue to cook, whisking frequently, until the sauce comes to a simmer and thickens, about 5-8 minutes.

Remove the sauce from the heat. Stir in the garlic powder, onion powder, salt, and pepper. Add 1 ½ cups of the shredded cheddar cheese and stir until the cheese is completely melted and the sauce is smooth.

In a large mixing bowl, combine the cooked chicken, cooked rice, fresh broccoli florets, and the sautéed onion and garlic mixture.

Pour the creamy cheese sauce over the mixture in the bowl and stir gently until everything is evenly coated.

Transfer the mixture to your prepared casserole dish and spread it into an even layer. Sprinkle the remaining ½ cup of cheddar cheese over the top.

In a small bowl, combine the Panko breadcrumbs and the 2 tbsp of melted butter. Toss to coat, then sprinkle the breadcrumbs evenly over the casserole.

Bake uncovered for 25-30 minutes, or until the casserole is hot and bubbly and the topping is golden brown.

Remove from the oven and let the casserole rest for 5-10 minutes before serving. This allows it to set up slightly.