Preheat your oven to 350°F (175°C). This ensures that your bake cooks evenly and thoroughly.

In a large mixing bowl, combine the cooked rice, cooked chicken, and frozen peas. Stir until well mixed.

In a medium saucepan over medium heat, melt the butter. This will serve as the base for your cheese sauce.

Once melted, whisk in the flour and cook for about 1 minute, stirring constantly. This creates a roux that thickens the sauce.

Gradually add the milk while whisking continuously to prevent lumps. Continue to cook until the mixture thickens and bubbles, about 5-7 minutes.

Remove from heat and stir in the mozzarella cheese, garlic powder, onion powder, salt, and pepper until the cheese is melted and the sauce is smooth.

Pour the cheese sauce over the chicken and rice mixture in the large bowl. Stir until everything is evenly coated.

Transfer the mixture to a greased 9x13 inch baking dish, spreading it out evenly.

Sprinkle the shredded cheddar cheese on top for a delicious cheesy crust.

Bake in the preheated oven for 25-30 minutes, or until the top is golden and bubbly.

Remove from the oven and let it cool for 5 minutes before serving. This helps the dish set and makes it easier to serve.