To make the pastry, rub 225g cold, diced butter into 350g plain flour, then mix in 100g golden caster sugar and a pinch of salt. Combine the pastry into a ball – don’t add liquid – and knead it briefly. The dough will be fairly firm, like shortbread dough. You can use the dough immediately, or chill for later. Preheat the oven to 200C/gas 6/fan 180C. Line 18 holes of two 12-hole patty tins, by pressing small walnut-sized balls of pastry into each hole. Spoon 280g mincemeat into the pies. Take slightly smaller balls of pastry than before and pat them out between your hands to make round lids, big enough to cover the pies. Top the pies with their lids, pressing the edges gently together to seal – you don’t need to seal them with milk or egg as they will stick on their own. (The pies may now be frozen for up to 1 month). Beat 1 small egg and brush the tops of the pies. Bake for 20 mins until golden. Leave to cool in the tin for 5 mins, then remove to a wire rack. To serve, lightly dust with icing sugar.