Begin by placing the chicken breasts in the bottom of the slow cooker.
Add the sliced carrots, chopped celery, diced onion, and minced garlic over the chicken.
Pour in the chicken broth and add the thyme, parsley, bay leaf, and black pepper. Stir gently to combine all ingredients.
Cover the slow cooker with the lid and set it to cook on low for 6 hours.
After 6 hours, carefully remove the chicken breasts and shred them using two forks. Return the shredded chicken to the slow cooker.
Add the egg noodles and frozen peas to the soup. Stir to incorporate and allow to cook for an additional 15-20 minutes, or until the noodles are fully cooked.
Taste and adjust the seasoning with salt and more black pepper if needed.
Serve the soup hot, garnished with fresh parsley if desired.
Store leftovers in the fridge for up to 3 days or freeze for longer storage.
For extra flavor, consider adding a squeeze of lemon juice before serving.