Add olive oil and butter to a large soup pot over medium-high heat. Once melted, toss in the chopped onion, sliced carrots, and chopped celery. Sauté for about 5–7 minutes until tender and fragrant.
Stir in the minced garlic and cook for an additional 30 seconds.
Pour in the chicken broth and water while adding in the uncooked chicken breasts along with Italian seasoning.
Increase the heat until the mixture comes to a gentle boil. Once boiling, reduce the heat slightly, cover with a lid slightly ajar, and let it simmer for about 15 minutes.
Stir in the egg noodles. Cook uncovered for another 8 minutes while stirring occasionally.
Carefully remove the cooked chicken breasts from the pot, shred or cut them into bite-sized pieces, and return them to the pot.
Season the soup with salt and pepper according to taste and sprinkle with freshly chopped parsley before serving.