In a large pot, melt the butter and add in the onions, carrots and celery. Cook until soft and fragrant. Add in the garlic and cook for another 30 seconds. Add the flour, salt and herbs and cook, stirring constantly, for a couple of minutes.
Add in the broth and shredded chicken. Bring to a simmer. Meanwhile, make the dumplings. In a large mixing bowl, whisk together the flour, baking powder, salt, and herbs. Pour in the milk and melted butter and stir with a wooden spoon until a shaggy dough forms. Using your hands, knead into a dough ball until all of the flour is incorporated. If the dough is too dry, add more milk as needed, 1 tablespoon at a time.
Using a cookie scoop, portion the dumplings and plop them into the summering soup. Cover and let simmer for 15 minutes. Be sure to keep covered the whole time so the dumplings steam. Remove from heat, give the soup and stir and enjoy!