Begin by setting the oven to preheat at 350°F (175°C) to ensure it is ready when the casserole is assembled.

In a medium saucepan, bring 1.5 cups of water to a rolling boil. Add the instant rice, stir to distribute evenly, then cover the pan. Remove from heat and allow the rice to absorb the water for approximately 5 minutes. Once done, fluff the rice with a fork to separate the grains.

Transfer the cooked rice into a large casserole dish. Add the cubed chicken and broccoli florets, and mix gently to ensure an even distribution of chicken and broccoli throughout the dish.

In a mixing bowl, combine the condensed cream of broccoli soup, milk, Italian-seasoned bread crumbs, garlic powder, and ground black pepper. Stir thoroughly until the mixture is smooth and uniform. Add half of the shredded Cheddar cheese to the mixture and stir until well incorporated.

Pour the prepared creamy sauce over the rice, chicken, and broccoli in the casserole dish. Mix gently to coat all ingredients with the sauce, ensuring even distribution.

Evenly sprinkle the remaining shredded Cheddar cheese over the top of the casserole mixture to create a golden, melted cheese layer when baked.

Place the casserole dish in the preheated oven, uncovered. Bake for approximately 30 minutes, until the dish is heated through and the cheese on top is melted and bubbling with a light golden hue.

Once removed from the oven, let the casserole sit for about 5 minutes before serving to allow it to set and make portioning easier.