Preheat oven to 200 degrees celsius. Line two baking trays with baking paper and set aside.
Lay the puff pastry sheets onto the bench and allow to defrost.
Add the olive oil to a frying pan over medium heat. Add the bacon, onion and garlic and cook for 5 minutes or until soft and fragrant. Place on to paper towel to remove any excess oil. Set aside to cool.
Place the spring onions, chicken mince, breadcrumbs, grated cheese and salt and pepper into a large bowl. Add the cooled bacon mixture. Mix until well combined.
Cut each pastry sheet in half. Spread one-sixth of the mixture along the middle of each pastry half.
Brush the whisked egg along one side of the mixture.
Roll the pastry over the mixture, placing the seam face-down. Cut the roll into 4 equal pieces.
Place onto the baking tray, lightly brush the milk over the pastry.
Repeat with remaining mixture and pastry sheets.
Bake in the oven for approximately 25 minutes or until golden and cooked through.
Leave to cool on the trays for 5 minutes before transferring to a wire rack to cool completely.
Serve immediately or store in an airtight container in the freezer for up to 3 months.