To make soup:
Put Double Chicken Stock in a large pot and heat, adding the diced carrots, celery, dill and parsley. Shred the reserved chicken breast meat into large pieces and add to the stock. Simmer over low heat for 5 minutes to cook the vegetables and reheat the chicken. Season to taste and serve as is, or ladle each serving over two warm matzo balls and garnish with a couple snips of dill.
For the matzo balls:
Mix matzo meal, eggs, chicken fat, salt, pepper and 2 tablespoons chicken stock in a bowl. Cover and place in the refrigerator for 30 minutes. Bring the rest of the chicken stock to a brisk boil in a medium pot. Reduce the flame. Run your hands under water so they are thoroughly wet. Form matzo balls by dropping spoonfuls of matzo ball batter approximately 1-inch in diameter into the palm of your wet hands and rolling them loosely into balls. Drop them into the simmering stock 1 at a time. Cover the pot and cook for 30 to 40 minutes.
*Find recipe for the double chicken stock recipe here.