Add the oil, butter, onion, carrots, and celery to a soup pot. Sauté over medium-high heat for 5-7 minutes.
Stir in the garlic and cook for 30 seconds or so.
Add in the chicken broth, water, chicken breasts, and Italian seasoning.
Turn the heat up to high and bring the soup to a boil, and once it's boiling, reduce the heat, cover the pot (with the lid slightly ajar), and simmer for 15 minutes.
Stir in the noodles and cook for another 8 minutes, with the lid off, stirring occasionally so the noodles don't stick to the bottom of the pot. You may need to turn the heat up a bit again so it's boiling gently.
Take the chicken out of the pot and cut it up/shred it, then add it back in. It should be cooked through, but you can always give it a few more minutes if it's not (chicken is safe to eat at 165F).
Season the soup with salt & pepper as needed (I am generous with both) and add in the fresh parsley.