Rub both sides of spareribs with the salts, sugar and cinnamon.
Cut apples into sixths.
Make sandwiches of the racks of ribs, a pair at a time, using apples and prunes, mixed, as the filling. Tie securely to retain the filling.
Brown in butter in a roasting pan, basting with enough warm water to cover the bottom of the pan. Cook slowly for 2½ hours in an oven preheated to 275-300 degrees. Add warm water from time to time if necessary to keep ribs from sticking and scorching.
Remove from oven and keep hot while you make the gravy. Add flour to the stock in the pan, stirring until smooth. Place pan over low heat on top of the stove. Slowly add the milk and cream. (If gravy becomes too thick, add more milk.) Stir until it comes just to the boiling point. Season with salt and pepper to taste.
Place spareribs on a serving platter. Remove string. Pour a small amount of gravy over the ribs, and serve the rest in a gravy boat to be savored over small boiled potatoes.
This recipe is always a huge hit. I don't bother cutting into individual servings before cooking. Two slabs tied together works very well, and keeps the fruit from falling all over the oven!