Homemade Chicken and Dumplings

Name: Homemade Chicken and Dumplings
Ingredients: 1 5-6 pound whole chicken (cut up); 16 cups water; 2 celery stalks (coarsely chopped); 2 carrots (coarsely chopped); 1/2 large onion (sliced); 3 garlic cloves (cut in half); 2 tablespoons kosher salt; 1 teaspoon peppercorns; 3 sprigs of fresh thyme; 1 sprig fresh rosemary; 3 cups all- purpose flour + more for rolling dumplings; 2 teaspoons baking powder; 1 teaspoon kosher salt; 1 egg (beaten); 1 cup reserved chicken broth; 1 cup of milk; 1 cup heavy cream; 1 teaspoon fresh ground pepper