For apples: Combine sugar, butter, salt, and cinnamon and fill apple core hollows with this mixture, reserving some to sprinkle on top. Roll out dough to ¼ inch thick and cut into 4 squares. Place an apple onto each square and spread remaining sugar mixture over apples. Bring up corners of dough to cover apple and press edges together (dampen with a little water if necessary). Make sure edges are sealed or dumplings will pop open during baking. Brush with egg white and prick tops of dumplings with a fork. Carefully transfer dumplings to a baking pan. Bake for 10 minutes, then reduce heat to 350 degrees F and continue baking for about 40 minutes longer, or until apples are tender when tested with a wooden pick. Serve with cream.