Place the chopped potatoes, celery, and onions in a large pot. Add the broth, pepper, and garlic powder. Bring to a boil, then reduce to a simmer.
Cover and cook until vegetables are tender, about 15-20 minutes. Do not overcook.
Add 1 cup milk and the chopped ham to the pot. In a bowl, stir together 2 Tablespoons flour, 1 cup milk, and 1 cup sour cream until blended. Add this mixture to pot.
Cook until thickened, stirring frequently, for about 10 minutes. .
Notes
Store leftovers in the refrigerator. They should stay fresh for about 4 days.You can leave the ham out if you like, or add bacon instead.