Pour the soup mic and chicken broth in the slow cooker, and mix together. Whisk in the cornstarch and pepper.
Add the carrots, celery, chicken and mix to combine.
Place the lid on the slow cooker and cook for 2-2 1/2 hours on high, or 4 hours on low.
For the dumplings, in a medium sized bowl, mix ingredients together until dough is soft.
Fill a large pot halfway full of water, and bring to a boil.
Drop spoonfuls of dough into the boiling water and let cook for 15 minutes, working in batches.
Remove the dumpling and place in the slow cooker and continue to cook for an additional 30 minutes on high or 1 hour on low.
Stir and enjoy.