In a large stockpot, melt butter then sauté onion, carrots, and celery until soft and tender, about 5 minutes. Add the chicken in and sprinkle with Italian seasoning. Cook until chicken has mostly cooked through, about 5 minutes.
Add in the chicken stock, water, dried sage, salt, and bay leaf. Bring to a boil then let simmer for 30-40 minutes.
In the last 5 minutes of cooking, add in the egg noodles.
Taste and adjust seasonings as needed.
Serve hot.
Store in an airtight container in the refrigerator for up to a week.