Prepare the Chicken: Season the chicken thighs with salt, pepper, thyme, and parsley. If you are using bone-in chicken, make sure the skin is crispy by patting it dry with paper towels. Preheat the air fryer to 400°F (200°C).
Cook the Chicken: Place the chicken thighs in the air fryer basket, skin side up. Cook at 400°F for about 20 minutes, or until the chicken reaches an internal temperature of 165°F (74°C). If using boneless thighs, reduce the cook time by about 5 minutes. Remove the chicken from the air fryer and set it aside.
Prepare the Broth: In a large pot or pan, add the chopped onion, garlic, celery, and carrots. Sauté for about 5-7 minutes until the vegetables are softened. Pour in the chicken broth, and bring to a simmer. Season with salt, pepper, thyme, and parsley, and let it simmer for another 10 minutes.
Make the Dumplings: In a large mixing bowl, combine the flour, baking powder, salt, and garlic powder. Add the butter and mix until the dough resembles coarse crumbs. Pour in the milk, and stir until just combined. Be careful not to overmix.
Form and Cook the Dumplings: Scoop the dumpling dough into small spoonfuls and drop them into the simmering broth. Cover and let them cook for 10 minutes without lifting the lid. Once the dumplings are cooked, gently add the chicken back into the pot to warm through.
Serve: Once the chicken is fully heated and the dumplings are fluffy, serve the dish immediately. Garnish with fresh parsley and enjoy!