In a saucepan, add Olive Oil (1 tablespoon) and Yellow Onion (1). Cook over a medium-high heat for 2-3 minutes, or until the onions have softened.
Add Ground Beef (500 gram). Cook, stirring, for 4 minutes, or until the beef has started to brown.
Add Corn Starch (1 tablespoon), Beef Stock (3/4 cup), Worcestershire Sauce (2 tablespoon), Ketchup (3/4 cup), and Salt and Pepper (to taste). Stir together. Reduce the temperature and allow to simmer for 8 minutes, or until the mixture thickens. Take off heat and set aside.
Using small pie plates as an outline, cut 4 circles from the Frozen Shortcrust Pastry (2 sheet), and 4 circles from the Puff Pastry (2 sheet). Press shortcrust pastry circles into each of the lightly greased pie plates.
Divide the meat mixture between the 4 pies. Brush edges of pastry with some of the Egg (1). Cover each pie with a puff pastry circle and press down around the edges to seal.
Cut a vent hole in the top of each pie and brush with remaining egg. Transfer pies to a metal oven tray.
Bake at 220 degrees C (425 degrees F) for 20-25 minutes, or until the pastry is puffed and golden.
Leave pies in their tins for 5 more minutes.
Top each pie with Tomato Sauce (to taste). Serve and enjoy!