Australian Savoury Pie

Name: Australian Savoury Pie
Cuisine: European
Ingredients: 500g ground beef (preferably 80% lean); 1 medium onion, finely chopped; 2 garlic cloves, minced; 1 tbsp vegetable oil; 1 tbsp all-purpose flour; 1 cup beef stock; 2 tbsp Worcestershire sauce; 2 tbsp tomato paste; 1 tsp pepper; Salt to taste; Optional ½ cup diced mushrooms for extra flavour; 2 sheets of shortcrust pastry (for the base); 2 sheets of puff pastry (for the top); 1 egg, beaten (for egg wash)