In a large mixing bowl, combine the chopped spinach, chopped artichoke hearts, cream cheese, mozzarella, Parmesan, sour cream, garlic powder, onion powder, and black pepper. Mix well until all ingredients are thoroughly combined and creamy.
Roll out the puff pastry on a lightly floured surface. Cut the pastry into 3-inch squares.
Place a tablespoon of the spinach and artichoke mixture in the center of each pastry square.
Fold the corners of the pastry over the filling to create a pocket, pinching the edges to seal securely.
In a small bowl, whisk the egg and brush it over the tops of each pastry for a golden finish.
Arrange the filled and brushed pastry bites on a baking sheet lined with parchment paper.
Bake in the preheated oven for about 15-20 minutes or until the pastry is golden brown and flaky.
Once baked, remove from the oven and allow to cool for a few minutes.
Garnish with freshly chopped parsley before serving.