Combine chicken, onion, carrots and celery in a large pot. Season to taste.
Add chicken broth. Bring to a boil, reduce heat, and simmer covered 45-60 minutes or until chicken is tender. While broth is simmering, prepare dumplings below.
Remove chicken and vegetables from broth. Discard skin and bones and chop remaining chicken, set aside.
Gently add dumplings to broth. Simmer 15-20 minutes or until tender.
Stir chicken (and vegetables if desired) into broth and cook about 2-3 minutes or until heated through.
Combine flour, baking powder, salt and shortening with a fork until shortening is mixed in.
Add milk a little at a time and mix until combined (you may not need all of it, you want a soft but not sticky dough).
Knead a few times on a floured surface until dough is smooth.
Generously flour your surface and roll the dough out to 1/8″ thick. Cut dough into 1″ x 2″ strips. Flour generously to avoid sticking.
Cook in broth as directed above.
TO THICKEN BROTH (OPTIONAL)
In a small bowl combine 4 tablespoons cornstarch with 4 tablespoons water.
Add to boiling broth a little bit at a time stirring to reach desired consistency.
Carrots and celery can be served on the side or chopped and added to the broth along with the chicken.
Nutrition information provided is an estimate and will vary based on cooking methods and brands of ingredients used.