In a large Dutch oven or heavy-bottomed pot, melt 1 tablespoon of butter over medium heat and sauté onion, carrots, and celery for 5-7 minutes until softened.
Add garlic, thyme, and rosemary, cooking for another minute until fragrant.
Pour in the chicken stock and add the chicken breasts; bring to a boil, then reduce heat and simmer for 15-20 minutes until chicken is cooked through.
Remove chicken to a plate, shred with two forks, and return the shredded meat to the pot.
In a medium bowl, whisk together flour, baking powder, salt, and pepper for the dumplings.
Stir in the milk and 3 tablespoons of melted butter until a thick, sticky dough forms.
Drop rounded tablespoons of the dough into the simmering soup, ensuring they are spaced apart.
Cover the pot tightly with a lid and simmer on low heat for 15 minutes without lifting the lid.
Garnish with fresh parsley and serve immediately.