Cut chicken breast, onion, king oyster mushroom, and bell pepper into bite-sized pieces.

Heat a pan with a small amount of oil and sauté the chopped onion first.

Add chicken breast to the pan and stir-fry until fully cooked.

Add king oyster mushroom and bell pepper to the pan and stir-fry together.

Add Worcestershire sauce and stir well. Substitute with soy sauce if unavailable.

Add tomato spaghetti sauce and mix thoroughly. Substitute with ketchup if needed.

Add cooked rice and butter to the pan and stir-fry until well combined.

Add shredded pizza cheese and stir until melted. Optionally, add a splash of milk or cream for a creamier texture.

Transfer the fried rice mixture to a baking dish, top with mozzarella cheese, and bake in the oven or microwave until the cheese is melted.