Preheat your oven to 400 degrees Fahrenheit and line a large baking sheet with parchment paper. Lightly flour your work surface and gently roll out one sheet of puff pastry into a large rectangle. Place this sheet onto the prepared baking sheet to make the assembly process easier later on.
Spread the basil pesto evenly across the surface of the puff pastry, leaving a very small border around the edges. Sprinkle the shredded mozzarella and parmesan cheese over the pesto. Top the cheese with a light dusting of garlic powder and dried oregano for extra aromatics.
Place the second sheet of puff pastry directly on top of the cheese layer. Using a sharp knife or a pizza cutter, cut the pastry into a large triangle shape to represent a Christmas tree. Use the leftover scraps of pastry to cut out a small star shape for the top of the tree and a small rectangle for the trunk at the bottom.
On both sides of the triangle, cut horizontal slits about one inch apart, making sure to leave the center of the tree intact to act as the trunk. Take each strip or branch and twist it away from you two or three times. This creates the beautiful spiral effect that exposes the green pesto and melted cheese inside.
In a small bowl, whisk the egg and water together to create an egg wash. Brush the entire surface of the tree and the star with the egg wash to ensure a golden, shiny finish. Bake in the oven for 18 to 22 minutes, or until the pastry is puffed and deep golden brown. Let it cool for five minutes before serving to allow the cheese to set slightly.
