Add the beef mince and diced onion to a large frying pan and cook over medium heat until the mince is browned, breaking up any large pieces as it cooks.
Add the onion powder, garlic powder, mixed herbs, Worcestershire sauce, tomato paste, water and brown sugar. Stir until well combined.
Reduce the heat and simmer, stirring regularly, until the mixture is thick and saucy with no excess liquid remaining.
Remove from the heat and allow the mince mixture to cool slightly.
Preheat the oven to 180°C fan bake and line baking trays with baking paper.
Lay the pastry sheets on the bench and cut each sheet into four equal squares.
Spoon 2–3 Tbsp of the mince filling into the centre of each pastry square, then sprinkle a little grated cheese over the top.
Fold the pastry edges up and pinch them together securely to form individual pies.
Place the pies onto the prepared baking trays and bake for 20–25 minutes, or until the pastry is puffed, crisp and golden.
Allow to cool for a few minutes before serving.