Using a large stock pot add diced carrots, onion and celery with 2 of the cartons of chicken stock (equals 64 oz) and 8 cups of the water and 1 tablespoon salted butter along with 1/4 teaspoon garlic powder and 1/4 teaspoon onion powder also 1 teaspoon sea salt and 1 teaspoon fresh coarsely ground black pepper. Bring to a boil then turn to just under medium high heat keeping at a boil for one hour. While chicken is boiling you can make the dough for the dumplings (After an hour remove chicken to cool. Once cooled tear into small bite sized pieces and add back to the broth.)
To make the dumplings.
Using a large mixing bowl whisk flour, salt, parsley flakes, onion powder and garlic powder. Add milk and eggs. Cut softened butter into pieces and add to flour mixture.
Flour your hands then knead until a loose dough forms. Dough should still stick to your hands but easily come off. Divide dough in two and form 2 balls picking up all the loose pieces. Wrap each ball in plastic wrap (Glad or Saran) tightly and refrigerate for an hour (although the dough can stay in the refrigerator up to overnight). The chicken should be done cooking while the dough is resting so this would be a good time to take out and let cool so you can debone it then add it back to the pot.
When you are ready for the dough lightly flour your surface and rolling pin. Dough might crumble a bit. just make into a tighter ball and roll the ball in the flour you've floured your surface with. Start to roll dough out to 1/4 inch. Using a pizza cutter or sharp knife cut dough into 1 inch pieces.
Bring broth up to hard boil and add the last 32 oz box of chicken broth and the last 3 cups water. Start adding dumplings quickly. Make sure that all dumplings are dunked under the surface a couple times. Let boil but stir frequently to keep dumplings from sticking to each other or the bottom of your pot. Your chicken should have been added back to the pot by this time if you haven't already done so add it back now.
Cook dumplings for 20 minutes. Take out one dumpling and test to see if it's done. It should be firm but still soft not gooey. Cooking time will vary due to thickness of dumplings. If not done at 20 minutes let cook an additional 10 minutes and check again.