For the shortcrust pastry, mix flour, 125 g sugar, 1 sachet vanillin sugar, baking powder and salt in a mixing bowl. Add 2 eggs and fat in flakes and knead with the dough hooks of the hand mixer.
With floured hands knead to a smooth dough. Cover the dough and chill for about 15 minutes. Roll out 2/3 of the dough into a circle (34 cm Ø) on a well floured work surface. Place in a tart tin (29 cm Ø) lined with baking paper with a removable base.
Slightly press down the bottom and edge. Prick several times with a fork. Refrigerate again for about 20 minutes. Put the rest of the dough in a cool place. In the meantime wash, peel and halve apples, cut out the core.
Cut apple halves into cubes. Wash mint, dab dry, pluck leaves from the stalks and cut into strips. Stir 50 ml apple juice and pudding powder until smooth. Boil up apples, apple juice, remaining vanilla sugar and other sugar.
Reduce at low heat for about 10 minutes. Boil up again and stir in the sauce powder. Bring to the boil and remove from the stove. Fold in mint strips. Roll out the rest of the shortcrust pastry on a floured work surface to form a lid (29 cm Ø) and prick several times.
Sprinkle the short pastry base with breadcrumbs. Spread apples evenly on top. Press the short pastry edge slightly towards the middle of the apples. Separate the rest of the egg. Whisk the egg white. Brush the edge of the pastry with it.
Place the lid on top and press down the rim. Bake the cake in the preheated oven (electric: 175 °C/ gas: level 2) on the lowest rack for approx. 45 minutes. Whisk egg yolk and cream. 10 minutes before the end of the baking time, coat the lid with egg yolk.
Take the cake out of the oven and let it cool down on a grid. Serve decorated with mint and apple as desired. Serve with whipped cream.