1. Butter a tart mold or pie plate; roll out the puff pastry and line the mold; prick all over with a fork to prevent it from swelling up;
2. brush the edges with an egg yolk beaten with 1 tbsp. water; 
3. fill with the pastry cream; 
4. arrange the apple slices on the pastry cream in a rosette pattern; sprinkle with sugar; 
5. bake in a preheated 220° C (450° F) oven for about 25 minutes. 

Serving 

1. Serve warm or cold; 
2. flambé with calvados if desired; 
3. whip the cream with the sugar and top each slice with a spoonful of whipped cream just before serving. 

Variation

1. combine 125 ml (1/2 cup) brown sugar with a little melted butter and a pinch of flour; 
2. sprinkle over the pie before baking.