Preheat oven to 180 C / Gas 4. Line a tart tin with greaseproof paper.
Roll out puff pastry and line the tin with it. Prick pastry several times with a fork. Fill with dry beans and bake in the preheated oven for 12 to 15 minutes. If the pastry balloons up during baking, flatten it with a spoon.
Peel apples and remove cores. Slice very thinly and mix in a bowl with lemon juice.
Arrange the apples slices on the pre-baked pastry in a decorative pattern.
In a bowl beat eggs and sugar, then add calvados and, creme fraiche and ground almonds.
Spread over the apples and bake for 15 minutes.
Sprinkle the tart with flaked almonds.
Return the tart to the oven and bake till golden brown, about 30 further minutes. Dust with icing sugar just before serving.