Prep the base: Add onion, carrots, celery, and garlic to the Crock Pot. Pour in the chicken broth.
Season the pot: Stir in bay leaves, thyme, parsley, rosemary (if using), salt, and pepper.
Add the chicken: Place the chicken breasts or thighs on top of the vegetables.
No need to cut—shredding later is easier.
Slow cook: Cover and cook on Low for 6–7 hours or on High for 3–4 hours, until the chicken is fully cooked and tender.
Shred the chicken: Remove the chicken to a cutting board and shred with two forks. Discard bay leaves.
Cook the noodles: Turn the slow cooker to High. Stir in egg noodles and cook for 15–20 minutes, or until al dente. (Check at 12 minutes—no one likes soggy noodles.)
Finish the soup: Stir the shredded chicken back in.
Add butter or olive oil if you want extra richness. Squeeze in lemon juice for brightness. Taste and adjust salt and pepper.
Serve: Ladle into bowls and sprinkle with fresh parsley.
Add cracked black pepper to finish.