2) To make a sandwich, warm a cast iron skillet over medium heat. Then, lay two slices of ham on the bread. Place a layer of apple slices over the ham and then spoon about a quarter of the filling on one side of the bread, making sure it's evenly spread. Cover with the other slice of bread.
3) Coat the top slice of bread with a very thin coating of mayonnaise, about 1 teaspoon.
4) Place the sandwich in the skillet, mayonnaise-coated side down. Weigh down with another small cast iron skillet, if you have one. After 45 seconds, slather the uncoated side of the sandwich with a similarly thin layer of mayo. Flip. Wait another 30-45 seconds and remove to your cutting board. Slice in half. Repeat with the rest of the sandwiches and serve.