Make dough first: Add flour, baking powder, 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 and mix with a wooden spoon. Add tablespoons of water one at a time until dough can be rolled into a ball.
Meat: Dice onions (and peppers if you want) and fry 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 (maggi) 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 frozen veg and cook with meat and spices for a further 5 minutes. After meat has browned well, put aside to cool.
In another pot, dice potatoes and boil for about 5 minutes so that they become soft; drain. Add potatoes to meat and mix.
Preheat oven to 180 C / Gas 4.
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 dough circle and pinch sides together with a fork.
Lightly brush tops of pies with the rest of the beaten egg. Place on baking parchment and place in oven for 25 minutes or until slightly brown.
Be very careful the amount of water you put at a time or dough can become sticky. If it becomes sticky or too soft, put it in the fridge for about 10 minutes for it to cool.
Serve with plantains or eat as a snack.
You can use mashed potato if you have no potatoes. Make half a cup of mash potato and add to meat as in step 6.