Make pastry first: Add flour, baking powder and salt to a bowl then rub in the butter. This will give a crumbly mixture. Beat the egg and add half to the flour and butter mixture then mix with a wooden spoon. Add tablespoons of water one at a time until dough can be rolled into a ball.
Meat: Sauté onion in oil for a few minutes. Add a little water to soften then add mince and mash in the pan with the back of the wooden spoon. Add stock cubes, black pepper and any other spices you want to.
When cooking meat and onions, only add a little bit of water as it needs to be dry when put on the dough. Add veges then cook with meat and spices for a further 5 minutes. After meat has browned well, put aside to cool.
In another saucepan, dice potatoes and boil for about 5 minutes so that they become soft; drain. Add potatoes to meat and mix. Preheat oven to 180 degrees C.
Flour worktop and roll out dough until it is about 2mm thick. Cut circles in the dough and place 1 or 2 teaspoons of meat in the centre of the circle. Fold dough over making it into a semicircle. Moisten edges of pastry circle and pinch sides together with a fork. Lightly brush tops of pasties with the rest of the beaten egg. Place on baking paper lined baking tray then place in oven for 25 minutes or until slightly brown.