Heat oven to 400 Fahrenheit.
Line a baking sheet with parchment paper and set aside.
On a floured surface, slightly roll out the puff pastry.
Cut each puff pastry sheet into four squares and place on the sheeted tray. You should have eight squares.
In the middle of each pastry square, add 3 to 4 spinach leaves, ¼ cup of shredded mozzarella, a few slices of the tomato, some of the grated Parmesan, basil, salt, pepper, and chilli flakes.
Take two opposite corners of the puff pastry and fold them over towards the centre, pressing the edges together to secure them.
Brush each pastry with egg wash and bake for 13 to 15 minutes, or until the puff is golden brown.
Remove from oven and drizzle with pesto oil.