Mix the sugar, cornflour and star anise together, then add the cherries and toss together.
Roll out two-thirds of the pastry thinly on a lightly floured surface. Use to line 4 fluted loose-bottomed 10 cm (4 inch) tart tins, rerolling the pastry trimmings as needed.
Spoon the cherry mixture into the pastry cases, and brush the top edges with milk or beaten egg. Roll out the reserved pastry with any trimmings and and cut 4 x 10 cm (4 inch) circles with a fluted biscuit cutter.
Add the pie lids and press the pastry edges together to seal. Slash the tops with a knife, then brush the tops with milk or beaten egg and sprinkle with a little extra sugar.
Bake in a preheated oven, 180°C (350°F), Gas Mark 4, for 20–25 minutes until the pastry is golden. Leave to stand for 15 minutes, then loosen the edges of the pies and take out of the tin. Serve warm or cold with custard.