In a large saucepan, cook and stir the pepper and onion in 1 tablespoon oil for 3 to 4 minutes until soft. Add the mince and stir until browned. Stir in the stock and ketchup and simmer over a low heat for 30 minutes.
Blend the plain flour with the water and add to the mince mixture along with the chilli powder. Simmer for a further 2 minutes, stirring constantly.
Roll out the pastry and cut out 4 circles using an inverted saucer. Place a spoonful of the meat mixture on each half of a circle. Wet pastry edges and fold over to form semi-circles. Press edges together to form a good seal. Cut small slits in top of each. Place patties on a baking tray lined with parchment.
Bake in the preheated oven for 20 to 25 minutes until golden brown.