Preheat your oven to 375°F (190°C) and line a baking sheet with parchment paper.

In a large mixing bowl, combine shredded mozzarella, ricotta, cottage cheese, feta, fresh spinach, sliced Castelvetrano olives, and kosher salt. Mix well until blended.

Roll out the thawed puff pastry sheets slightly smaller than the baking sheet. Lay one sheet on the lined baking sheet.

Spread the cheese and spinach filling over the pastry, leaving half an inch at the edges. Lay the second piece of pastry on top, sealing the edges securely.

Score the top layer into diamond shapes, making shallow cuts to allow steam to escape.

Whisk together the remaining egg and heavy cream for an egg wash, and brush over the top.

Sprinkle desired toppings over the washed pastry and bake for 50-55 minutes until golden brown.

Let cool for 5-10 minutes before cutting along the scored lines and serving warm.