Toss the apple slices in the lemon rind and juice. Heat the butter in a large frying pan, add the apples, sugar and orange rind and cook gently for 5 minutes until the apples are softened but still hold their shape.
Mix the cornflour with the orange juice, add to the pan with the sultanas and cook until the juices have thickened. Take off the heat and leave to cool.
Reserve one-third of the pastry, then roll out the remainder thinly on a lightly floured surface. Stamp out 12 × 10 cm (4 inch) circles with a plain biscuit cutter and press into a buttered 12-section muffin tin.
Spoon the apple filling into the pie cases, doming it up high in the centre. Roll out the reserved pastry and any pastry trimmings, then cut out 12 × 7 cm (3 inch) lids with a fluted biscuit cutter. Brush the pie edges with milk, then press the lids on the pies. Reroll the trimmings and cut small decorations. Brush the tops of the pies with milk, add the decorations and brush these with egg or milk, then sprinkle with a little caster sugar.
Bake in a preheated oven, 190°C (375°F), Gas Mark 5, for 25 minutes until the pastry is golden. Leave to stand in the tins for 20 minutes, then loosen the edges with a knife, lift out of the tins and serve warm with custard.