Step 1: Preheat oven to 375°F (190°C) and grease a 9x13-inch baking dish.
Step 2: In a large skillet over medium heat, cook ground beef until browned. Drain excess fat.
Step 3: Add diced onion and minced garlic to the skillet. Sauté for 3–4 minutes until soft and fragrant.
Step 4: In a large bowl, combine cooked rice, steamed broccoli, cheddar cheese, Parmesan cheese, cream of mushroom soup, milk, salt, black pepper, paprika, and garlic powder. Stir in the cooked ground beef mixture.
Step 5: Transfer the mixture into the prepared baking dish and spread evenly.
Step 6: Sprinkle shredded mozzarella cheese over the top.
Step 7: Bake for 25–30 minutes or until the casserole is bubbly and the cheese is melted and golden.
Step 8: Remove from oven and let rest for 5 minutes before serving.