Add berries, sugar, and water to cast iron pot. Bring to a boil.
Reduce heat and simmer 10 minutes.
Mix flour, shortening, and milk to form dumpling dough.
Drop dough onto simmering berries.
Cook uncovered 10 minutes, then covered 10 more minutes.
Add water if berries thicken too much.
Serve warm, topped with ice cream or whipped cream.