Remove the dough from the fridge about 10-15 minutes before rolling to prevent it from cracking.
Preheat the oven to 375f and set one rack to the lowest level and the second to the middle level. Grease a (9 by 3") springform pan with butter or lard.
Roll out the larger ball to a circle approximately 1/4-inch thick and about 15-inches round. Place the dough into the pan and tuck in the edges letting the excess overhang. Trim off the excess overhanging dough. Any open spots should be patched with the excess dough.
Pour the filling into the pie pan, leaving at least a 1/4-inch unfilled. If needed, use a spatula to level out the filling.
Roll out the second smaller ball to a circle a bit larger than the pie pan. Cut into 1-inch wide strips for a lattice.
Place the strips in a lattice formation about a 1-inch apart. Make sure to overlap the dough so that the strips stay down while baking. Alternatively, you can forgo the lattice and just cover the pie with the second circle and cut a slit for venting. The choice is yours.
Use your fingers or a fork to press the strips down into the corners so that they stick. If needed a touch of water can be used to "glue" the strips to the sides. Cut off any excess dough.
Beat the egg yolk with 2 teaspoons of water and brush the top of the pie crust.
Bake for 20 minutes on the lowest rack, then move the pan up to the middle rack and continue baking. Full bake time will be approximately 60-70 minutes. Check the pie at the halfway point and if it looks like it's getting too brown cover loosely with foil. Once golden brown, remove from the oven and place on a wire rack to cool.
After baking, let the pie cool for 2 hours before removing the sides of the springform. The pie can be eaten the same day though it's better to let it sit overnight in the refrigerator. Place the pizzagaina in the oven at 350f for a few minutes the next day. The heat will slightly melt the butter and allow easy removal of the bottom pan plate.
Pizzagaina is best made the day before and eaten the next day after it has settled and cooled. It can be served either cold or warm. Enjoy!