Season the mince with salt and pepper. Heat up a large pan on a medium-high heat and add the oil. Once the pan is hot, add half of the mince and brown. Break up the mince to smaller pieces. Once browned, transfer the mince to a large bowl and repeat the browning with the remaining uncooked mince. Transfer to the large bowl.
Next, add the onions and cook until translucent. Add the garlic and cook for a minute. Put the browned mince back into the large pan. Sprinkle the flour over the minced beef and onions and toss to coat.
Stir in tomato puree and add the stock. Add the mixed herbs and Worcestershire sauce and bring to a boil. Once it's started to boil, transfer to the lowest heat and let it simmer for around 45 minutes. Stir very often so that the mince doesn't start to burn. At the very end, season with salt and pepper to your liking. Let the filling cool.
When the filling is cooling, start preparing the pastry. Leave the shortcrust pastry and puff pastry on the counter to defrost. Preheat the oven to 220 C (430F).
Get your 4 pie moulds (mine are 13cmx3cm). Find a round bowl that is larger than your pie mould and cut out 4 circular pieces of shortcrust pastry. Press the shortcrust pastry into the pie moulds. Trim the excess pastry and poke some holes in the bottom using a fork. Place some baking paper into each pie mould and place baking beans on top of the baking paper. Blind bake in the preheated oven for 10 minutes.
Take the baking paper and baking beans out. Fill each pie with mince filling, be careful not to overfill. Place the grated cheese on top of the mince filling. Cut out four circular pieces of puff pastry using the same bowl as before and place it on top of the pie filling. Trim the excess pastry, crimp the edges using a fork and poke two holes in the centre using your fork. Brush the beaten egg on top of each pie and crack some pepper on top of each pie.
Bake in the oven for 15 minutes. Serve hot with tomato sauce. These pies can be frozen in an airtight container for up to 3 months. Heat in the oven before serving the frozen pies.
* Percent Daily Values are based on a 2,000 calorie diet. Your daily value may be higher or lower depending on your calorie needs.