Warm the brandy in a saucepan, add the prunes, simmer gently for 3–4 minutes, then take off the heat. Pour the cream and milk into a second saucepan, add the vanilla pod and bring just to the boil, then take off the heat. Cover both pans and set aside for 2 hours.
Meanwhile, roll the pastry out on a lightly floured surface to fit a buttered 24 cm (9½ inch) fluted loose-bottomed tart tin, then press the pastry over the base and sides. Trim off the excess pastry with scissors so that it stands a little above the top of the tin. Prick the base with a fork and chill for 15 minutes.
Bake the tart case blind (see
Whisk the eggs and sugar together in a large bowl until creamy. Retrieve the vanilla pod, scrape out the seeds and add the seeds to the eggs, then whisk in the milk mixture.
Drain the prunes, adding excess brandy to the milk mix, then arrange in the base of the tart case. Pour over the custard and bake for 25–30 minutes until the custard is pale golden and just set. Leave to cool, then remove from the tin and dust with icing sugar to serve.