Roll out dough (on little flour) rectangular (about 32 x 16 cm for 250 g dough), cut into squares (number = 2 x servings). Place on a baking sheet lined with parchment paper, cool for about fifteen minutes.
Roll out marzipan on a little powdered sugar into a rectangle (about 16 x 8 cm at 80 g), cut into squares. Cover dough squares with one marzipan square and apple slices each. Lightly score dough around apples.
Brush edges of dough with egg, sprinkle with sugar and score a few times on each of 2 sides. Spread butter flakes evenly on apple slices.
Bake: about fifteen min in the middle of the oven heated to 220 °C.
Cream: Stir apple juice up to and including sugar well with whisk in chrome steel frying pan. Bring to a boil over medium heat, stirring throughout (see note). Remove skillet from heat, continue stirring for about two min, pour into a large enough bowl. Cool, fold cream and calvados into cream, set aside to cool with lid closed.
Serve: Decorate crem with flaked almonds. Dust apple jalousies with powdered sugar, bring to table with it.
Note: ‘bring to a boil’ means heat to just below boiling point. If the cream is not heated enough, it will remain thin.