Load the crockpot: Add carrots, celery, onion, garlic, bay leaves, thyme, parsley, rosemary, salt, and pepper. Place the chicken on top.
Pour in the chicken broth to cover everything.
Set and cook: Cook on Low for 6–7 hours or High for 3–4 hours, until the chicken is very tender and the vegetables are soft.
Shred the chicken: Remove the chicken to a cutting board and shred with two forks. Discard any large fat pieces if using thighs. Return the chicken to the crockpot.
Add noodles: Stir in the egg noodles.
Cook on High for 15–20 minutes, or until the noodles are just tender. Stir once halfway through to prevent clumping.
Finish the flavor: Stir in lemon juice and butter or olive oil if using. Taste and adjust with more salt and pepper.
Remove bay leaves.
Serve: Ladle into bowls and top with fresh parsley. Add extra broth if you prefer a soupier bowl.