Preheat the oven to 180C/350F/Gas 4.
For the pastry, combine the flour, baking powder and salt in a mixing bowl.
Cut the lard and butter into 1cm/½in cubes, add to the flour, and rub the fat into the flour until it resembles fine breadcrumbs. Add just enough cold water to form a soft dough. Wrap in cling film and set aside in the fridge to rest for an hour.
For the empanada filling, heat one tablespoon of oil in a large frying pan, sprinkle the stock cube into the hot oil and fry for 30 seconds, stirring continuously. Add the steak and fry for about two minutes until brown. Set the meat and the juices to one side.
Heat the remaining tablespoon of olive oil, add the onion and green pepper and fry until soft, about three minutes. Add the garlic and fry for a further minute. Add the wine, cumin, paprika, chilli powder, olives and the salt and freshly ground black pepper. Fry for a further minute, stirring continuously. Return the meat and juices to the pan and stir well. Set aside to go cold.
To fill the empanadas, take the pastry out of the fridge, and on a well-floured surface, roll out a thin sheet. Using a saucer as a template, cut out discs of pastry.
Place a tablespoon of the filling on one half of the pastry circle. Brush the edge with egg, fold over and crimp the edges together.
Brush with egg and place on a greased baking sheet. Bake for 20 minutes, or until golden-brown.
Serve either hot or cold as a snack or starter.