Place the olive oil in a large deep pot (that has a lid) over medium heat. Add the diced onion and minced garlic to this and cook for 2-3 minutes or until they become fragrant.
Add the chopped chicken breasts and cook for 4-5 minutes on one side. Flip and cook the other side of the chicken for another 4-5 minutes or until each side is slightly browned on the outside. To help speed up the process, you can place the lid on top and allow the chicken to steam for a 3-4 minutes on each side. The chicken doesn’t have to be fully cooked through, since it will continue cooking along with the orzo.
Pour in the dry orzo and stir well.
Add the chicken broth or stock. Stir well and make sure the orzo doesn't stick to the bottom of the pot. Cover the pot with the lid, bring to a boil and then reduce to a simmer and cook for 15 minutes (stirring every 5 minutes to make sure the orzo doesn’t stick to the bottom) or until the orzo has soaked up the liquid and the chicken has cooked to an internal temperature of 165°F (73.9°C).
Add the lemon zest, lemon juice, freshly grated parmesan, fresh spinach, basil, salt and pepper. Stir and cook on low for another 3-5 minutes or until the cheese has melted and the spinach has wilted.
Serve immediately with a sprinkle of extra parmesan and fresh basil or parsley. Season with salt and pepper and enjoy!