Preheat the oven to 200°C and lightly grease a baking tray.
Apple pastries: Cut 8 circles, each 8 cm in circumference, from the puff pastry.
Prick with a fork and place on the prepared baking tray.
Place the apple slices on the pastry circles.
Brush with butter and sprinkle with caster sugar.
Bake for about 15 minutes or until the pastry is crisp and brown.
Custard filling: Heat the milk to just under boiling point.
Beat the egg yolks, sugar, cornflour and salt together and gradually stir in the milk.
Heat at very low temperature until the custard thickens, stirring constantly.
Remove from the heat and stir in the vanilla essence.
Allow to cool.
Caramel sauce: Melt the butter and sugar over low heat, stirring constantly.
Keep stirring until a rich caramel colour is obtained.
Remove from the stove and carefully stir in the cream.
Return to the stove and simmer for 5 minutes, stirring constantly.
To serve: Place 4 of the pastries on dessert plates, spoon some of the custard mixture on top and cover with the remaining pastries.
Dust with icing sugar and serve with cream or ice cream and the caramel sauce.