Ingredient:   Pie Filling: 1 tbsp olive oil 1 large brown onion, peeled and chopped 500 g (1.1 lbs) braising beef, cut into bite-sized chunks 1 tbsp plain (all-purpose) flour ¼ tsp salt ¼ tsp black pepper 600 ml (2.5 cups) hot beef stock (made with 2 stock cubes dissolved in water) 2 la…