First prepare the shortcrust pastry. To do this, work the flour into the butter until a fine crumbly mass is formed. This is best done with a food processor and a coarse whisk.
Add the sugar, egg and milk (use a dough hook if necessary) to make a firm shortcrust pastry.
Put the dough in plastic wrap for about 1/2 hour in the refrigerator to rest (if you need to make it quickly, you can do without it, in which case you can add 1/2 package of baking powder to the dough).
Peel apples with a hard skin, remove the core and finely slice. Stew in 250 ml apple juice until soft. If the apples are rather sour, add about 3-4 tablespoons of sugar. Then add cinnamon and rum.
Prepare a thick pudding from 500 ml apple juice with 2 pkg. vanilla pudding powder according to package instructions. Mix the pudding with the stewed apples.
Preheat the oven to 200 °C top and bottom heat. Roll out the dough and line the bottom and sides of a springform pan with it.
Pre-bake the dough for 10 minutes. Pour the still hot apple-pudding mixture into the pre-baked dough and bake for 30 minutes at 200 °C top and bottom heat. Allow to cool.
Spread whipped cream on the cold cake.