Process basil, garlic, and part of the olive oil into a paste, adding oil gradually. Mix in Parmesan and salt.
Cut puff pastry into 10x40cm strips, roll into cylinders.
Spread filling on each cylinder, fold sides to center, then fold in half to form a 2.5x40cm roll. Repeat with remaining strips.
Freeze cylinders for 2 hours. Preheat oven to 200°C (392°F). Slice into 1-1.5cm pieces, place on greased baking sheets, and bake for 15-20 minutes until golden.
Serve warm or store in a covered container for up to 3 days.
Notes
For a crispier crust, brush with egg wash before baking.