Preheat your oven to 400°F (200°C). Unroll the puff pastry on a lightly floured surface.
In a mixing bowl, combine butter, garlic, parsley, salt, and black pepper. Mix until smooth.
Spread the garlic butter mixture over the puff pastry, then sprinkle mozzarella and Parmesan cheese evenly.
Fold the puff pastry in half, pressing down to seal. Cut slits on top to allow cheese to ooze out.
Transfer to a parchment-lined baking sheet and bake for 20-25 minutes until golden brown.
Allow to cool for a few minutes, slice, and serve warm.