Heat the olive oil or butter in a large soup pot over medium heat.
Add the onion, carrots, and celery, then cook for 6 to 8 minutes until the vegetables start to soften.
Stir in the garlic, thyme, dried parsley, salt, pepper, and bay leaf. Cook for about 30 seconds, just until fragrant.
Pour in the chicken broth and bring the soup to a gentle boil.
Add the shredded chicken and egg noodles.
Reduce the heat to a steady simmer and cook until the noodles are tender, about 8 to 10 minutes.
Remove the bay leaf and stir in the lemon juice, if using.
Taste and adjust the seasoning, then finish with fresh parsley before serving.