Clean and grate the apples on a coarse grater. Sprinkle them with a little of the sugar and leave them to release their juice.
Crumble the biscuits in a bowl, add the nuts which you've chopped or blended in a blender, and the raisins.
Melt the butter and pour it over the biscuits while it's still hot. Stir everything.
Drain out the juice from the apples and add them to the biscuit mixture.
Add the rest of the sugar, cinnamon and sour cream.
Stir again and pour it into an 11″ (28 cm) diameter form with removable sides, even it out and grate chocolate for decoration.
Cover the form with plastic wrap and leave in the fridge for 12 hours.