1. Bring the chicken broth and bay leaf to a simmer in a stockpot over medium-low heat for 1 hour. Remove the bay leaf. Add the leeks and carrots and bring to a simmer again, cooking until the vegetables are tender, about 10 minutes. Keep hot.

2. Sift the flour, baking powder, pepper, nutmeg, mace, cinnamon, and salt together in a large mixing bowl, and set aside. Toss the bread and buttermilk together. Let bread soak for 10 minutes. Mash, and add the chicken, chopped ginger, egg, and scallions. Sift in the flour mixture, and stir to mix well. Shape into small balls, using about 2 tablespoons of dumpling mixture for each.

3. Bring a large saucepan of water to boil, and add 2 tablespoons salt. Poach the dumplings in two batches, stirring occasionally, about 5 minutes each batch. Dumplings will float when cooked. Serve dumplings in soup bowls with hot broth.