Preheat oven to 180°C and line two baking trays with baking paper.
Place frying pan over medium heat and add oil. Saut the onion and garlic until golden brown then add the spinach and saut for about 5 minutes. Place the mixture into a strainer and gently squeeze to remove any excess liquid.
Place mixture into a bowl and stir through the cheeses, herbs, salt and pepper.
Slice sheets of pastry in quarters and evenly distribute the mixture amongst the pastry sheets to form a thin sausage shape.
Roll the pastry sides to a close, making sure it overlaps underneath.
Place onto the prepared trays and bake for 30 minutes.
Once golden brown, remove the trays and place on racks to cool for a few minutes before serving.