Place diced celery and onion to the bottom of the crock pot.
Add chicken breasts on top of celery and onion.
Sprinkle garlic salt on chicken breasts.
Add cream of chicken soup.
Add chicken broth.
Add butter on top and sprinkle pepper.
Cook on LOW for 6 hours.
After 6 hours, chicken should be tender. Use a sturdy spatula/spoon to shred chicken. It should fall apart when you press on it. Continue until all chicken is shredded.
If the broth needs to be thickened (it usually does), add a little cornstarch/water mixture to thicken a bit.
If you are adding mixed vegetables, go ahead and add to the pot.
Take biscuits and cut into small squares (3-4 cuts across and once down the middle). Add to the pot and mash them down just enough to moisten the top of the dough. OPTIONAL- save a couple biscuits to cook on the side to eat with the meal.
Cook on HIGH for 1.5-2 hours. Check the center of one of the biscuit dumplings to ensure they are cooked all the way through.
Stir the pot and serve.