Place the chicken, onions, carrots, and celery in a large stock pot and cover with water. Cook chicken for 2-3 hour. When you have about 30 minutes left on the chicken start making your dumplings.
Mix flour, baking soda, and salt together in bowl. Cut shortening into flour mixture with your fingertips until it resembles small peas. Add milk a quarter cup at a time, you may not need a full cup.
Stir until a ball of dough just begins to form, being careful not to over mix. On a flour surface roll about 1/4 inch thick.
Using a pizza cutter cut dough into rectangles about 1 inch wide by 2 inches long. Place strips on flour sheet pan and allow to harden for at least 30 minutes or up to several hours.
Once chicken is done, remove from the broth and let cool. Remove chicken from the bone and shred into medium-sized pieces, discarding bones and skin. Strain broth & bring to a boil.
Cover and allow to cook for 7-10 minutes. Reduce heat to low and add chicken. Allow to cook until thickened, about 20 to 30 minutes.
Season generously with salt and pepper. Enjoy!