Begin by preheating your oven to 200 degrees Celsius. Take a large mixing bowl and therein combine the pork mincemeat with the French onion soup mix, tomato ketchup, Worcestershire sauce, and Dijon mustard. Make sure to season the mixture adequately with black pepper.

Proceed to prepare the puff pastry. Lay out the pastry sheets and cut each sheet in half. You will then distribute the meat mixture evenly down the length of each pastry half, forming it into a log shape.

In a small bowl, whisk together the egg and milk. Use this mixture to brush along one side of the pastry, adjacent to where the meat mixture is placed. Carefully roll the pastry over the meat, ensuring that it is fully encased, and press gently to seal the edges.

With a small serrated knife, slice each log into either six or eight pieces, depending on your preference. Arrange these pieces on a baking tray that has been lined with baking paper.

Place the tray in the preheated oven and bake the rolls for a duration of 20 to 25 minutes. The rolls should achieve a golden brown color and be cooked thoroughly before removal from the oven.