Preheat you oven to 150° C/ 300° F.
Sprinkle the bottom of the pie with the ground hazelnut.
Peel and or the apples and cut them into wedges. Depending on the size of the apple 6-8 wedges per apple, sprinkle with ½ of the sugar and the cinnamon and marinated for approximately 15 minutes, then layer into the pie crust fairly tightly.
Cut the excess dough around the edge of the pie mold off.
Place in the oven at 150° C/ 300° F for approximately 15 minutes or until the apples are starting to soften. Remove and set aside to cool.
In a bowl, beat the egg and the remaining sugar until the sugar has been resolved and the mixture is pale and foamy. Add the flour to the mixture and incorporate without lumps. Add d the heavy cream. And the Calvados to taste at the very end. Brandy or Cognac can be substituted.
Pour the cream/flour batter into the pie, covering the apples approximately 2/3.
Bake in the oven at 180° C/ 356° F for approximately 15 minutes.
Sprinkle with some excess sugar and bake for another 15 minutes or until the apples are soft, the mixture well set, the pie golden brown and the sugar caramelized.
Un-mold the tart and let to cool on a wire rack and serve slightly warm.