Make sure the butter and water are cold before making the pastry.
Finely dice the butter, add it to the flour and rub with your fingertips until the mixture resembles fine breadcrumbs. Make a well in the centre of the bowl and add most of the water and a pinch of salt.
Mix the dough without overworking it. You just want to bring the ingredients together.
Roll the mixture into a ball, flatten slightly and cover with cling film. Allow to rest in the fridge for at least 30 minutes. When the filling is cooked, roll the pastry into a circle the size of a dinner plate and about 5 millimetres thick.
The pastry can last for approximately four days in the fridge or you can freeze it for use at a later date.
Preheat the oven to 180'C.
Peel and cut the onion, carrot and potato into 1cm dice.
Cook the potato in boiling water until tender.
Heat a large saucepan over a medium heat and add a drizzle of oil. Add the mince to the pan and cook until browned. Add the onion, carrot, Worcestershire sauce and the stock. Season with salt and pepper and then reduce the heat to a simmer and then for 90 minutes, adding a little water if the sauce becomes too thick. You are looking for the sauce to become a rich, thick gravy. Remove the mixture from the heat and add the cooked potato and the peas. Allow to cool.
Beat the egg and brush it on to the edge of pastry circles. Add 3 or 4 tablespoons of the filling and then bring two sides of the pastry together so they meet in the middle. Crimp the edges together to seal the pastry. Try to avoid trapping lots of air inside the pastry.
Place the pasties on a lightly oiled baking tray and brush with the egg wash. Bake in the oven for 25 minutes or until golden brown.
«Traditionally, Cornish pasties were made with a savoury filling in one half and sweet in the other. Try using an apple pie filling if you want to replicate this. »