Prepare the broth: Pour the 6 cups of chicken broth into a large pot or Dutch oven. Bring to a gentle simmer over medium heat. You want small bubbles breaking the surface, not a rolling boil. Maintain this temperature throughout cooking.
Make the dumpling dough: In a large mixing bowl, whisk together the flour, baking powder, and salt until evenly combined. Make a well in the center and pour in the milk all at once. Using a wooden spoon or your hands, stir until the mixture comes together into a shaggy dough. Don't overmix - some flour streaks are fine. The dough should be slightly sticky but manageable.
Rest the dough: Cover the bowl with a clean kitchen towel and let the dough rest for 5-10 minutes. This crucial step allows the flour to fully hydrate and the gluten to relax, making the dough easier to roll and resulting in more tender dumplings.
Roll and cut the dumplings: Generously flour your work surface and turn the dough out onto it. Dust the top with more flour. Using a rolling pin, roll the dough out to an even ½-inch thickness - this exact thickness is key to authentic texture. Using a pizza cutter or sharp knife, cut the dough into approximately ½-inch squares. Don't worry about perfect uniformity; rustic squares are authentic.
Cook the dumplings: Drop the dumpling squares one by one into the gently simmering broth, stirring gently after every few additions to prevent sticking. Once all dumplings are in, reduce heat slightly to maintain a gentle simmer (not a boil). Stir frequently - every 3-5 minutes - to prevent sticking to the bottom. Simmer uncovered for 25 minutes. The broth will thicken considerably as the dumplings release their starch.
Add the chicken: After 25 minutes, when dumplings are tender and broth is beautifully thickened, gently stir in the cooked chicken pieces. Continue cooking for an additional 5 minutes to heat the chicken through.
Season and serve: Taste and adjust seasonings as needed. Add black pepper, additional salt, poultry seasoning, or fresh herbs to your preference. The dish will continue to thicken as it sits. Serve hot, garnished with fresh parsley if desired. Ladle into bowls and enjoy immediately for the best texture.