Add the 1 1/2 pounds boneless, skinless chicken breasts, 1 cup onion, 2 stalks celery, 2 medium carrots, 3 cloves garlic,1 teaspoon salt, ½ teaspoon pepper, 4 cups chicken stock, 2 cups water, and 1 bay leaf to your slow cooker.
Cover and cook the broth on LOW for 6 hours or HIGH for 4 hours.
In a mixing bowl, combine the 2 cups matzo meal, 2 teaspoons baking powder, 2 teaspoons salt1 teaspoon pepper, 1/2 cup water, 1/2 cup vegetable oil, and beaten 8 large eggs.
Mix thoroughly until well combined, then refrigerate the mixture for at least 30 minutes to firm up.
Once chilled, roll the mixture into small, uniform balls and place them back into the refrigerator until the soup is ready.
Carefully remove the chicken from the slow cooker, shred the meat using two forks, and return the shredded chicken to the pot. Remove and discard the bay leaf.
About 30 minutes before serving, gently drop the chilled matzo balls into the simmering soup.
Cover the slow cooker and continue cooking for the final 30 minutes, or until the matzo balls are light and cooked through.
Ladle the soup into bowls, Parsley for garnish and serve immediately.