Preheat the oven to 400 degrees. Line a baking sheet with parchment paper.
Unfold the puff pastry sheet and cut into thirds, then in half. You should have 6 rectangles. Arrange them on the parchment lined baking sheet so that they’re not touching. Use the butterknife to make a score mark all the way around each pastry ¼-½ inch from the edges.
In a medium/large bowl, mix together the spinach, chopped artichoke hearts, cream cheese, and mozzarella cheese.
Fill the center of each pastry with the mixture.
Whisk the egg in a small bowl.
Use a pastry brush to brush the egg onto the edges of each pastry.
Transfer the baking sheet to the oven and bake for 15-17 minutes, until golden.
Serve these warm and enjoy!