Cook the Chicken: Heat a large skillet over medium-high heat and add diced chicken seasoned with salt and spices. Sauté for about 8–10 minutes until golden brown and cooked through. Set aside.

Prepare the Rice: In a separate saucepan, bring 2 cups of water and ¾ teaspoon of salt to a rolling boil. Add 1 cup of long-grain rice, reduce heat, cover, and simmer for 18-20 minutes until water is absorbed. Fluff with a fork.

Make the Cheese Sauce: In a deep skillet, melt 6 tablespoons of unsalted butter over medium heat. Add ¼ cup diced onions and celery, sauté for 4-5 minutes. Stir in 2 teaspoons minced garlic, cooking for 1 minute.

Thicken the Sauce: Sprinkle 4 tablespoons flour over the mixture, stirring for 2 minutes. Gradually whisk in 2 cups chicken broth and 1½ cups whole milk, cooking for 5-7 minutes until the sauce thickens.

Add the Cheese: Reduce heat to low, stir in 1 cup cheddar cheese until melted. Season with additional black pepper, garlic powder, and celery salt.

Combine Ingredients: In a large bowl, combine cooked chicken, steamed broccoli, fluffy rice, and creamy cheese sauce. Mix until well combined.

Assemble the Casserole: Spread half of the mixture into a greased baking dish. Sprinkle half of the mixed cheese topping. Layer remaining mixture and top with remaining cheese.

Bake to Perfection: Preheat oven to 350°F (175°C) and bake for 20 minutes until heated through and cheese is bubbly. Optional: broil for 2-3 minutes for a golden finish.

Serve and Savor: Remove from oven, cool for a few minutes, slice, and serve warm.