Make the pastry: sift the flour into a bowl, add the butter and rub together using your fingertips until the mixture resembles fine breadcrumbs. Add 1 tbsp water and use a knife to bring the dough together, cutting and turning until it forms a ball. Add a little more water, if necessary. Wrap in cling film and chill in the fridge for 15 minutes.
Meanwhile, make the filling: heat the oil in a frying pan, add the onion, pepper and garlic, and cook for 10 minutes until soft. Add the beef and fry for another 10 minutes until browned.
Stir in the oregano, sugar and passata, and cook for a further 10 minutes, stirring occasionally. You may need to add a little water to loosen the mixture, but it should be fairly dry. Remove from the heat and set aside to cool.
Preheat the oven to 180°C, fan 160°C, gas 4. Grease 3 x 6-hole tart tins and set aside. Dust your work surface with flour and roll out the pastry to the thickness of a pound coin. Cut out 18 circles (large enough to line the tins), then gently press them in.
Spoon the mince filling into each pie. Roll out the leftover pastry and cut into small strips to make a cross top for each pie.
Brush the crosses with a little milk and bake in the oven for 15 minutes until the pastry is golden.
Cook's tip: if you don’t fancy making the pastry, you can use 375g ready-rolled shortcrust instead.