Start your fire and preheat your wood or gas-fired oven to approximately 350 deg F. Pus the fire and coals to the back or side of your oven and sweep the cooking floor.
Remove the dough from the refrigerator and roll out the dough so it is approximately a 12” circle.
Fold into quarters and gently transfer the dough to a cast iron pan. Unfold into the pan, allowing the extra dough to drape over the sides.
Make two to three circles of apple slices in the bottom, leaving a 1 ½” gap to the edge of the pan.
Pour any remaining spice mix juice over the apples.
Next, gently fold the crust over the outside edge of the apple layer, folding an overlap into the edges using your finger as a fulcrum every inch or two. (See video above for a demo of the technique.)
When the edges are all folded in, brush the beaten egg around the top and sides of the crust using a pastry brush, and then sprinkle decorative sugar crystals (your own desired amount) on top of the crust.
Bake for 25-30 minutes, or until the crust has browned and the apples are tender. Do keep an eye on your crostada, as the crust can scorch quickly if the heat flairs or the pan is too close to the fire. Using long, heat-resistant gloves, rotate your pan a few times during baking so that the edges are exposed evenly to the extra heat from the flames.
Remove from the oven and place on a cooling rack. Tip: Be sure to place the pan on a rack so that the bottom doesn’t get soggy during cooling, but note that is easier to remove the crostada from the cast iron pan while it is still a little warm to prevent the crust from sticking.