First, preheat the oven to 400° F.
Next, lay out a sheet of parchment paper and unroll the pizza dough onto it.
With the long edge facing you, sprinkle ¾ cup mozzarella cheese on the bottom. Top with the pepperoni, Italian seasoning, and parmesan cheese. Top with the remaining ¾ cup mozzarella cheese.
Next, fold the top half of the dough over to create what, at this point, essentially looks like a giant calzone. Press the edges together to seal.
Keeping the dough on the parchment paper, transfer it to a large baking sheet. Brush the beaten egg over the entire topside of the dough.
Bake for about 15 minutes, until golden brown.
Allow to cool for a bit and then cut crosswise into slices. Serve with warm marinara sauce.