Place the chicken in a Dutch oven with the parsley, rosemary, thyme, bay leaves plus the chopped celery and onion.
Add 8 cups of the chicken stock along with the chicken base, kosher salt, and pepper. Bring to a boil over medium heat then reduce the heat to medium-low, cover and simmer for 30 minutes.
Add the carrots and potatoes and continue cooking for about 45 minutes or until the chicken is cooked through and the vegetables are tender.
Remove the chicken from the stock and transfer to a pan until it’s cool enough to handle. Then remove the meat from the bone and shred or chop into bite size pieces.
Combine the remaining cup of stock with the milk and the 6 tablespoons of the flour. (If you like a thicker stock, add all the flour.) Whisk until the flour is completely dissolved. Pour the flour mixture into the stew, stirring to blend together. Cook over medium heat until the stock thickens, about 15 minutes.
Once the stock has thickened, add the chicken and the peas to the stew.
For the dumplings:
Combine the flour with the baking powder, poultry seasoning, ground sage, parsley, kosher salt, and pepper. Stir in ¾ cup milk and mix until blended, adding more milk if needed.
Using a small ice cream scoop or tablespoon, measure out the dough and gently drop the dumplings on top of the stew. Do not stir!
Cover the pan and cook over medium-low heat for 25 to 30 minutes or until the tops of the dumplings appear “dry” and no longer sticky to the touch.