Preheat the oven to 350°F (175°C).
In a medium saucepan, bring 1 1/2 cups of water to a boil. Stir in the Knorr Chicken Flavor Rice Mix, reduce heat to low, cover, and simmer for 15 minutes or until rice is tender and water is absorbed. Remove from heat and set aside.
While the rice cooks, heat olive oil in a large skillet over medium heat. Add the chicken pieces and cook for 6-8 minutes, stirring occasionally, until cooked through and no longer pink inside. Remove from heat.
Steam the broccoli florets until just tender, about 4-5 minutes. Drain and set aside.
In a large mixing bowl, combine the cooked rice, cooked chicken, steamed broccoli, cream of mushroom soup, sour cream, milk, garlic powder, onion powder, salt, and black pepper. Stir until well combined.
Fold in 1/2 cup of the shredded cheddar cheese and all of the mozzarella cheese.
Transfer the mixture to a greased 9×13-inch baking dish. Sprinkle the remaining 1/2 cup of cheddar cheese evenly over the top.
Bake uncovered in the preheated oven for 25 minutes or until the casserole is bubbly and the cheese on top is melted and lightly golden.
Remove from the oven and let rest for 5 minutes before serving.