Preheat the Oven:

1. Begin by setting your oven to 200°C (392°F) and preparing a baking sheet by covering it with parchment paper.

Prepare the Filling:

1. In a large bowl, combine the pork mince, French onion soup mix, ketchup, Worcestershire sauce, and Dijon mustard.
2. Combine the ingredients completely, ensuring they are evenly blended together.
3. This will ensure a flavorful filling for the rolls.

Assemble the Sausage Rolls:

1. Lay out the defrosted puff pastry sheets on a clean surface.
2. Divide the pork mixture into three equal portions. Place one portion of the pork mixture along one edge of each pastry sheet, shaping it into a log.

Roll and Seal:

1. Gently roll the pastry over the pork filling to encase it, sealing the edge with a little water if necessary. Once rolled, cut each log into smaller sections, about 6 to 8 pieces per roll, depending on your preferred size.

Egg Wash:

1. In a small bowl, whisk together the egg and milk to create an egg wash. Brush this over the top of each sausage roll, giving them a lovely golden finish when baked.

Bake:

1. Place the sausage rolls on the prepared baking tray, ensuring a little space between each one. Bake for 20-25 minutes or until the pastry is puffed up and golden brown, and the filling is fully cooked.

Serve:

1. Once baked, remove the sausage rolls from the oven and let them cool slightly before serving. These rolls are delicious hot or cold, making them perfect for any occasion!