In a large pot or Dutch oven, combine the chicken broth, diced onion, minced garlic, sliced carrots, chopped celery, dried thyme, and dried parsley. Bring to a gentle boil over medium heat.
Once boiling, add the chicken breasts to the pot. Reduce heat to a simmer and cover. Cook for 15-20 minutes, or until the chicken is fully cooked through.
Remove the chicken from the pot and let it cool slightly. Shred the chicken into bite-sized pieces using two forks and set aside.
In a mixing bowl, whisk together the flour, baking powder, and ½ teaspoon of salt. Stir in the milk and melted butter until just combined.
Return the shredded chicken to the pot and adjust seasoning with salt and pepper as needed. Bring the soup back to a simmer.
Drop spoonfuls of the dumpling batter into the simmering soup, ensuring they are spaced apart. Cover the pot and cook for an additional 10 minutes, allowing the dumplings to steam and rise.
Once the dumplings are fluffy and cooked through, remove from heat. Serve hot with a ladle, garnished with additional parsley if desired.