Pre-heat the oven to 180°C. Roll out the pastry on a lightly floured surface to 1cm thick and cut a round of pastry 3-4 inches larger than an 8 inch straight-sided tart tin. Line the tin with the pastry, pressing in well then prick the base. Trim any overhanging pastry and chill for 10 minutes.
Arrange the diced apple across the base of the pastry. Whisk together the egg, egg yolk and sugar until thick and creamy, then whisk in the cream, milk and vanilla extract until smooth.
Pour on top of the apples and into the pastry. Bake for 50-60 minutes until the filling is set and the pastry is golden and cooked. Remove and allow to cool in the tin before turning out and cooling completely on a wire rack. Cut into portions and serve on side plates. Dust very lightly with icing sugar before serving.