Remove pips from the boiled and cooled lemon halves.
Blend the lemon, raisins, sultanas, apple, mixed fruit, and peel into a paste.
Mix the fruit paste with suet, sugar, currants, spices, brandy, and sherry, then set aside overnight.
Grease muffin tins with butter to accommodate 15–18 pies.
Pulse flour, baking powder, butter, and sugar in a processor until the mixture looks like breadcrumbs.
Add orange zest and juice, blending until the mixture forms a dough.
Knead the dough briefly on a floured surface, wrap in plastic, and chill for 1 hour.
Preheat the oven to 200°C.
Roll half the pastry to 0.5cm thickness and cut 7cm discs for the muffin tin bases.
Fill each base with 1 tablespoon of mincemeat and brush the edges with beaten egg.
Roll remaining pastry to 0.5cm, cut 5cm discs, place on top, and seal the edges.
Brush the tops with remaining egg and poke a small steam hole in each pie.
Bake for 20–25 minutes until pale golden-brown.
Serve warm or cold with cream, brandy butter, or ice cream.