Preheat the oven to 220 degrees Celcius / 430 degrees Fahrenheit with top and bottom heat.
Roll out the puff pastry on the baking paper. Fold the edges up slightly if you’d like to create a decorative crust.
Brush the edges with the beaten egg yolk mixed with a splash of milk. Prick the center of the pastry with a fork. Optionally, sprinkle the edges with sesame seeds.
Pre-bake the puff pastry for 8 minutes.
Spread a thin layer of crème fraîche over the base, followed by a very light layer of green pesto.
Top with the mozzarella balls and halved cherry tomatoes. Bake for another 10–15 minutes, until golden brown and fully cooked.
Just before serving, add the Serrano ham, fresh arugula, and Parmesan shavings on top. Enjoy!