In your slow cooker, place the boneless, skinless chicken breasts along with chopped onions, sliced carrots, thinly sliced celery, and finely chopped garlic. Add the thyme and rosemary sprigs, along with a bay leaf for added flavor. To enrich the broth, toss in unsalted butter, kosher salt, and freshly ground black pepper. Stir gently to combine all the ingredients.

Cover the slow cooker and set it to High, allowing the mixture to cook for 2 hours. The chicken should become tender and fragrant while the vegetables soften.

After 2 hours, carefully open the slow cooker lid and pour in the low-sodium chicken broth. Stir to incorporate the broth with all the other ingredients. Close the lid again and continue cooking on High for an additional 30 minutes.

Once the cooking time is up, remove the chicken breasts from the slow cooker and shred the chicken into bite-sized pieces. Return the shredded chicken, discarding the thyme, rosemary, and bay leaf, and stir to distribute the chicken throughout the soup.

Add the wide egg noodles to the slow cooker, cover, and let them cook on High for about 20 minutes, or until they are al dente.

Once the noodles are done, stir the soup one last time. Ladle the soup into bowls and garnish with chopped fresh parsley.