Start by making the pie filling. In a large bowl or zip lock bag, toss together the pieces of chuck steak and the flour. In a frying pan or pressure cooker set to saute mode, heat the oil. Add the pieces of beef in batches, shaking off any excess flour, being careful not to overcrowd the pan. Cook for a few minutes until the outside has browned. Remove from the pan and set aside and repeat until all of the beef has been browned.
In the same pan, add the onion and garlic and saute until soft. At this stage, if you’re using a frying pan, transfer into a pressure cooker, otherwise add the beef back to the pot of the pressure cooker and turn off the heat. Add the remaining ingredients for the filling and mix to combine.
Place the lid on the pressure cooker and cook on manual for 45 minutes, releasing the pressure manually once complete.
Take the lid off and set the pressure cooker back to saute. You want to reduce the liquid a little bit so that the gravy is nice and thick - this should take about 10 minutes. Season with salt and ground black pepper to taste.
Turn off the pressure cooker and let the filling cool down before assembling the pies. You can even make this the day before and store in the fridge until ready to use.
To make the pies. Preheat the oven to 180°C and lightly spray two muffin tins with canola oil.
Using a large glass or mug, cut out circles of the shortcrust pastry to make the bases of the pies. Press each round of pastry into the muffin pan.
Spoon the filling into the pies until just full. Using a standard glass that’s about the same size as the top of each muffin hole, cut out circles of puff pastry. Press each circle over the filling and gently cut a slit in the top of each. Whisk an egg in a small bowl and brush over the top of each pie. Bake in the preheated oven for about 20-25 minutes or until a dark golden brown. Let cool in the pan for at least 10 minutes before turning out and serving with tomato sauce. Repeat if necessary to use up all of the pastry/filling.
Serve straight away or let cool completely before storing in the fridge or freezer.