In a large skillet, heat the olive oil over medium-high heat. Season the chicken with salt and pepper, then cook for 5-7 minutes, until browned and cooked through. Remove the chicken from the skillet and set aside.

In the same skillet, add the chopped onion and sauté for about 3 minutes until soft and translucent. Stir in the minced garlic and cook for an additional minute.

Add the orzo pasta to the skillet and cook for 2 minutes, stirring frequently to lightly toast it.

Pour in the chicken broth and milk, bringing the mixture to a boil. Once boiling, reduce the heat to low. Let it simmer uncovered for 10-12 minutes, stirring occasionally until the orzo is tender and most of the liquid is absorbed.

Return the cooked chicken to the skillet, adding the cheddar and Parmesan cheese. Stir well so the cheese melts and coats the chicken and orzo evenly.

Mix in the Italian seasoning and chopped spinach, then cook for another 2-3 minutes, just until the spinach wilts. Adjust seasoning with salt and pepper to your liking.

Remove the skillet from heat, allowing the dish to thicken slightly for a couple of minutes before serving. Garnish with fresh parsley if desired.